diff --git a/01-hello.rb b/01-hello.rb
index e0e7bbf..e04b69e 100644
--- a/01-hello.rb
+++ b/01-hello.rb
@@ -1,8 +1,8 @@
 # 题目: 输入名字，输出 "Hello, 名字"
 
 print "请输入你的名字，然后按 Enter: "
-your_name = gets
+zhoujin = gets
 
 # ...
 
-puts "(请替换成最后的答案)"
\ No newline at end of file
+puts "hello,#{zhoujin}"
diff --git a/02-variable.rb b/02-variable.rb
index a5a4753..3ec25fd 100644
--- a/02-variable.rb
+++ b/02-variable.rb
@@ -3,11 +3,10 @@
 a = 1
 b = 2
 
-puts "a 是 #{a}"
-puts "b 是 #{b}"
+puts "a = #{b}"
+puts "b = #{a}"
 
 # ...
 
 puts "a 应该是 2，现在是 #{a}"
 puts "b 应该是 1，现在是 #{b}"
-
diff --git a/03-triangle.rb b/03-triangle.rb
index fafec03..2362a80 100644
--- a/03-triangle.rb
+++ b/03-triangle.rb
@@ -7,5 +7,5 @@
 b = gets
 
 # .....
-
-puts "直角三角形的面积是: _________"
\ No newline at end of file
+s = a.to_f * b.to_f / 2 
+puts "直角三角形的面积是:#{s}"
diff --git a/04-pizzas.rb b/04-pizzas.rb
index 4c2521f..409537a 100644
--- a/04-pizzas.rb
+++ b/04-pizzas.rb
@@ -7,6 +7,7 @@
 people = gets
 
 # .....
-
-puts "每人可分得几片: _________ 片"
-puts "还剩下几片: _________ 片"
\ No newline at end of file
+a = pizzas.to_i / people.to_i
+b = pizzas.to_i % people.to_i
+puts "每人可分得几片: _#{a}片"
+puts "还剩下几片:#{b}片"
diff --git a/05-bmi.rb b/05-bmi.rb
index 67efdff..cf1b10c 100644
--- a/05-bmi.rb
+++ b/05-bmi.rb
@@ -11,7 +11,18 @@
 height = gets
 
 # .....
+bmi = ( weight.to_f * 10000/ ( height.to_f * height.to_f ) )
+puts "您的 BMI 是: #{bmi}"
 
-puts "您的 BMI 是: _________"
 
-puts "您的 BMI 结果是: _________(过轻或正常或过重)"
\ No newline at end of file
+
+
+if bmi < 18.5
+   puts "您的BMI结果是：过轻"
+
+elsif bmi >= 24
+   puts "您的BMI结果是：过重"
+
+else
+  puts "您的BMI结果是：正常"
+end
diff --git a/06-interger-positive.rb b/06-interger-positive.rb
index a240f5f..ff3b464 100644
--- a/06-interger-positive.rb
+++ b/06-interger-positive.rb
@@ -4,7 +4,17 @@
 print "请输入一个整数，然后按 Enter: "
 x = gets
 
-# ....
 
-puts "这个数是_____ (正数或零或负数)"
-puts "这个数是_____ (偶数或奇数)"
\ No newline at end of file
+if x.to_i > 0
+  puts "这个数是正数"
+elsif x.to_i == 0
+  puts "这个数是零"
+else
+  puts "这个数是负数"
+end
+
+if x.to_i % 2 == 0
+  puts "这个数是偶数"
+else
+  puts "这个数是奇数"
+end
diff --git a/07-abcde.rb b/07-abcde.rb
index 5d0c8c3..57fc8c9 100644
--- a/07-abcde.rb
+++ b/07-abcde.rb
@@ -9,14 +9,30 @@
 #     当 z < 0 输出 "E"
 
 print "请输入一个整数x，然后按 Enter: "
-x = gets
+x = gets.to_i
 
 print "请输入一个整数y，然后按 Enter: "
-y = gets
+y = gets.to_i
 
 print "请输入一个整数z，然后按 Enter: "
-z = gets
+z = gets.to_i
 
 # ....
 
-puts "结果是________(A或B或C或D或E)"
\ No newline at end of file
+if x > 0
+  if y > 0
+    if z > 0
+      puts "结果是B"
+    elsif z < 0
+      puts "结果是C"
+    end
+  elsif y < 0
+     if z > 0
+       puts "结果是D"
+     elsif z < 0
+       puts "结果是E"
+     end
+   end
+elsif x < 0
+      puts "结果是A"
+end
diff --git a/08-find-max.rb b/08-find-max.rb
index 9e6e643..cbfcb53 100644
--- a/08-find-max.rb
+++ b/08-find-max.rb
@@ -11,4 +11,11 @@
 
 # ....
 
-puts "最大的数是 ________(x或y或z)"
\ No newline at end of file
+
+if x >= y && x >= z
+  puts "最大的数是x"
+elsif y >= x && y >= z
+  puts "最大的数是y"
+else
+  puts "最大的数是z"
+end
diff --git a/09-function.rb b/09-function.rb
index b1f922d..8d9e6c8 100644
--- a/09-function.rb
+++ b/09-function.rb
@@ -1,15 +1,15 @@
 # 题目: 输入直角三角形的宽和高，输出三角形的面积
 
 def calculate_area(a, b)
-  # ....
+  a * b / 2
 end
 
 print "请输入直角三角形的高，然后按 Enter: "
-a = gets
+a = gets.to_i
 
 print "请输入直角三角形的底边，然后按 Enter: "
-b = gets
+b = gets.to_i
 
 answer = calculate_area(a,b)
 
-puts "直角三角形的面积是: #{answer}"
\ No newline at end of file
+puts "直角三角形的面积是: #{answer}"
diff --git a/10-function.rb b/10-function.rb
index bb450fb..708262e 100644
--- a/10-function.rb
+++ b/10-function.rb
@@ -1,19 +1,26 @@
 # 题目: 使用者输入 x,y,z，请输出三个数中最大的数
 
 def find_max(x, y, z)
+  if x >= z && x >= z
+    return x
+  elsif y >= x && y >= z
+    return y
+  else
+    return z
+  end
 end
 
 print "请输入一个数字x，然后按 Enter: "
-x = gets
+x = gets.to_f
 
 print "请输入一个数字y，然后按 Enter: "
-y = gets
+y = gets.to_f
 
 print "请输入一个数字z，然后按 Enter: "
-z = gets
+z = gets.to_f
 
 # ....
 
 answer = find_max(x,y,z)
 
-puts "最大的数是 #{answer}"
\ No newline at end of file
+puts "最大的数是 #{answer}"
diff --git a/11-seven.rb b/11-seven.rb
index 26c221d..afc26f9 100644
--- a/11-seven.rb
+++ b/11-seven.rb
@@ -3,7 +3,9 @@
 i = 1
 while ( i <= 100 )
 
-  # ....
+  if i % 7 == 0
+    puts i
+  end
 
   i+=1
-end
\ No newline at end of file
+end
diff --git a/12-sum-even.rb b/12-sum-even.rb
index 73879bb..35065d0 100644
--- a/12-sum-even.rb
+++ b/12-sum-even.rb
@@ -5,9 +5,11 @@
 
 while ( i <= 100 )
 
-  # ....
-
+  if i % 2 == 0
+    total += i
+  end
+  
   i+=1
 end
 
-puts total
\ No newline at end of file
+puts total
diff --git a/13-nn.rb b/13-nn.rb
index ac0a43b..e209fc5 100644
--- a/13-nn.rb
+++ b/13-nn.rb
@@ -1,11 +1,19 @@
 # 题目: 输入一个数字 N，输出 N * N 乘法表
 
 print "请输入数字 N，然后按 Enter: "
-n = gets
+n = gets.to_i
+i = 1
 
+while ( i <= n )
+  j = i
+  while ( j <= n )
+    puts " #{i} * #{j} = #{i*j}"
+    j += 1
+  end
+  i += 1
+end
 # while ( ... )
 #   while ( ...)
 #
 #   end
 # end
-
diff --git a/14-prime.rb b/14-prime.rb
index 8cf1692..ee539ea 100644
--- a/14-prime.rb
+++ b/14-prime.rb
@@ -1,7 +1,16 @@
 # 输入一个数字 N，请检查是不是质数
 
 def is_prime(n)
-# ....
+ i = 2
+ while ( i <= (n/2) )
+   if n % i == 0
+     return false
+     break
+   else
+     i += 1
+   end
+ end
+ return true
 end
 
 print "请输入数字 N，然后按 Enter: "
diff --git a/15-guess-number.rb b/15-guess-number.rb
index 48f9dca..8b7d869 100644
--- a/15-guess-number.rb
+++ b/15-guess-number.rb
@@ -5,13 +5,13 @@
 while (true)
   print "请猜一个 0~99 的数字 N，然后按 Enter: "
   n = gets
-
-  #puts "太低了，再猜一次"
-  #puts "太高了，再猜一次"
-
-  if n.to_i == target
+  if n.to_i < target
+  puts "太低了，再猜一次"
+elsif
+     n.to_i > target
+  puts "太高了，再猜一次"
+else n.to_i == target
     puts "恭喜猜中啦! "
     break
   end
-
-end
\ No newline at end of file
+end
diff --git a/16-array-sum.rb b/16-array-sum.rb
index 9b4910b..fbfcfaa 100644
--- a/16-array-sum.rb
+++ b/16-array-sum.rb
@@ -1,11 +1,16 @@
 # 给定一阵列内含数字，输出最大值
 
 def find_max(array)
-  #....
+  m = array[0]
+  array.each do |i|
+    if m <= i
+      m = i
+    end
+  end
+  m
 end
 
 arr = [8, 12, 36, 53, 9, 75, 3, 71, 59, 88]
 
 max = find_max(arr)
 puts "Max is #{max}" # 应该是 88
-
diff --git a/17-array-stats.rb b/17-array-stats.rb
index 0af81bb..d359dfa 100644
--- a/17-array-stats.rb
+++ b/17-array-stats.rb
@@ -14,7 +14,20 @@
 
 puts arr.to_s
 
-puts "总和是 _____"
-puts "平均是 _____"
-puts "最大值是 _____"
-puts "最小值是 _____"
\ No newline at end of file
+def sum(arr)
+  sum = 0
+  for i in arr
+    sum += i
+  end
+  return sum
+end
+
+def average(arr)
+  return sum(arr) /arr.size
+end
+
+
+puts "总和是 #{sum(arr)}"
+puts "平均是 #{average(arr)}"
+puts "最大值是 #{arr.max}"
+puts "最小值是 #{arr.min}"
diff --git a/18-square.rb b/18-square.rb
index 226e1c1..65ed3a8 100644
--- a/18-square.rb
+++ b/18-square.rb
@@ -3,8 +3,13 @@
 arr = []
 
 print "请输入数字 N，然后按 Enter: "
-n = gets
+n = gets.to_i
 
-# ...
+i = 0
+while ( i < n )
+  arr.push(i * i)
+  i += 1
+end
 
-puts arr.to_s
\ No newline at end of file
+
+puts arr.to_s
diff --git a/19-filter.rb b/19-filter.rb
index ef7e515..8295578 100644
--- a/19-filter.rb
+++ b/19-filter.rb
@@ -1,9 +1,15 @@
 # 给定一阵列内含数字，输出另一个数组只包含偶数
 
 def filter_even(arr)
-  #...
+   even_arr = []
+   arr.each do |n|
+     if (n % 2 == 0)
+       even_arr.push(n)
+     end
+   end
+   return even_arr
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
-puts filter_even(arr).to_s # 应该是 [68, 42, 46, 46, 86]
\ No newline at end of file
+puts filter_even(arr).to_s # 应该是 [68, 42, 46, 46, 86]
diff --git a/20-sorting.rb b/20-sorting.rb
index 5f82c08..d568d6f 100644
--- a/20-sorting.rb
+++ b/20-sorting.rb
@@ -2,10 +2,16 @@
 # Hint: 可用 arr.sort 排序，和 arr.uniq 去除重复
 
 def filter_even(arr)
-  #...
+  even_arr = []
+  arr.each do |n|
+    if n % 2 == 0
+      even_arr.push(n)
+    end
+  end
+  return even_arr.uniq.sort
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
 
-puts "________" # 应该是 [42, 46, 68, 86]
\ No newline at end of file
+puts filter_even(arr).to_s # 应该是 [42, 46, 68, 86]
diff --git a/21-selection-sort.rb b/21-selection-sort.rb
index e5e7eae..ec63a61 100644
--- a/21-selection-sort.rb
+++ b/21-selection-sort.rb
@@ -2,11 +2,28 @@
 # https://zh.wikipedia.org/wiki/选择排序
 
 def selection_sort(arr)
-  #...
+  temp = 0
+  i = 0
+  l = arr.size - 1
+  while ( i < l )
+    min = i
+    j = i + 1
+    while (j < arr.size )
+      if arr[min] > arr[j]
+        min = j
+      end
+      j += 1
+    end
+    temp = arr[min]
+    arr[min] = arr[i]
+    arr[i] = temp
+    i += 1
+  end
+  return arr
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
 answer = selection_sort(arr)
 
-puts answer.to_s # 应该是 [1, 7, 9, 42, 46, 46, 68, 77, 86, 91]
\ No newline at end of file
+puts answer.to_s # 应该是 [1, 7, 9, 42, 46, 46, 68, 77, 86, 91]