程序改错，c语言初学者，请各位大佬帮忙！！！谢谢！

Question

程序改错
1.程序功能：把一张百元钞票,换成一元、二元和五钞票,每种至少8张,求对换方案数。程序中有两行有错误。改正错误，使它能输出正确的结果。
Private Sub Command1_Click()
n = 0
'下一行程序有错！
For x = 1 To 100
For y = 8 To 50
For z = 8 To 20
'下一行程序有错！
If x + y + z = 100 Then n = n + 1
Next z
Next y
Next x
End sub
2.程序功能：计算y=1+2/3+3/5+4/7+…+n/(2*n-1)(n=50), 要求：按四舍五入的方式精确到小数点后第二位。程序中有一处错误。改正错误，使它能输出正确的结果。
Private Sub Command1_Click()
Dim s As Single
Dim n As Integer
s = 0
For n = 1 To 50
'下一行程序有错
s = s + n / 2 * n - 1
Next n
Print Round(s, 2)
End Sub

Answer 1

For y = 1 To 50
For z = 1 To 20

If x + y*2 + z*5 = 100 Then n = n + 1

s = s + n / (2 * n - 1)