#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define N 5/*计算的次数*/
int zcd()/*主菜单函数*/
{
        int i,a,b,c,d,m;/*a,b,c,d分别代表四个子菜单的开关*/
        printf("*********欢迎使用小学生算术软件**********\n");
        printf("1开始算术，0结束程序\n");
        scanf("%d",&i);
        if(i=1) printf("请选择您想完成的练习\n");
        printf("a:加法练习！   b：减法练习！    c：乘法练习！    d：除法练习！");
        scanf("%d",&m);
        if (m=a)
        return(1);
        if (m=b)
        return(2);
        if (m=c);
        return(3);
        if (m=d);
        return(4);
}
void chuti() /*加法出题函数*/
{int X,Y,n,a;
X=1;
Y=20;
srand((unsigned)time(NULL)); /*随机种子*/
n=rand()%(Y-X+1)+X; /*n为X~Y之间的随机数*/
switch(n)
{case 1: {printf("11+23=\n");break;}
 case 2: {printf("15+22=\n");break;}
 case 3: {printf("18+9=\n");break;}
 case 4: {printf("38+29=\n");break;}
 case 5: {printf("21+3=\n");break;}
 case 6: {printf("44+51=\n");break;}
 case 7: {printf("2+6=\n");break;}
 case 8: {printf("43+98=\n");break;}
 case 9: {printf("56+12=\n");break;}
 case 10: {printf("88+12=\n");break;}
 case 11: {printf("2+96=\n");break;}
 case 12: {printf("1+99=\n");break;}
 case 13: {printf("54+21=\n");break;}
 case 14: {printf("11+2=\n");break;}
 case 15: {printf("54+9=\n");break;}
 case 16: {printf("32+19=\n");break;}
 case 17: {printf("77+32=\n");break;}
 case 18: {printf("15+76=\n");break;}
 case 19: {printf("25+65=\n");break;}
 case 20: {printf("42+32=\n");break;}
}
}




main()
{       int i;
system("graftabl 936");
        srand(time(NULL));
        i=zcd();
        if(i=1) jiafa();


                printf("\n*******恭喜你通关完成*******\n");
        printf("谢谢使用本软件，再见！！");
}









int  jiafa(void)
{int n,X,Y,k,a;
for (k=0;k<=9;k++)
{chuti();
getch();
printf("请输入你的答案：");
scanf("%d",&a);
printf("%d",a);
} /*加法练习*/



}

if后面的括号里面判断是用==而不是赋值号=；呵呵呵

帮你改了一下，其他的你自己搞定啊。。

#include<stdio.h>
#include<stdlib.h>

#include<time.h>
#define N 5/*计算的次数*/
int zcd()/*主菜单函数*/
{
    int i  = 0,a = 0,b = 0,c = 0,d = 0 ;/*a,b,c,d分别代表四个子菜单的开关*/
    char m;
    printf("*********欢迎使用小学生算术软件**********\n");
    printf("1开始算术，0结束程序\n");
    scanf("%d",&i);
    if(i == 1) printf("请选择您想完成的练习\n");
    else if(i == 0) return 0;
    printf("a:加法练习！   b：减法练习！    c：乘法练习！    d：除法练习!\n");
    scanf("%s",&m);
    if (m =='a')
        return(1);
     else if (m =='b')
        return(2);
     else if (m =='c')
        return(3);
     else if (m =='d')
        return(4);
     else
        return(0);
}
void chuti() /*加法出题函数*/
{
    int X = 1,Y = 20,n = 0,a = 0;
    srand((unsigned)time(NULL)); /*随机种子*/
    n=rand()%(Y-X+1)+X; /*n为X~Y之间的随机数*/
    switch(n)
    {
    case 1: {printf("11+23=");break;}
    case 2: {printf("15+22=");break;}
    case 3: {printf("18+9=");break;}
    case 4: {printf("38+29=");break;}
    case 5: {printf("21+3=");break;}
    case 6: {printf("44+51=");break;}
    case 7: {printf("2+6=");break;}
    case 8: {printf("43+98=");break;}
    case 9: {printf("56+12=");break;}
    case 10: {printf("88+12=");break;}
    case 11: {printf("2+96=");break;}
    case 12: {printf("1+99=");break;}
    case 13: {printf("54+21=");break;}
    case 14: {printf("11+2=");break;}
    case 15: {printf("54+9=");break;}
    case 16: {printf("32+19=");break;}
    case 17: {printf("77+32=");break;}
    case 18: {printf("15+76=");break;}
    case 19: {printf("25+65=");break;}
    case 20: {printf("42+32=");break;}
    }
}

int  jiafa();
int main()
{
    int i;
    srand(time(NULL));
    i=zcd();
    if(i==1)
        jiafa();
    printf("\n*******恭喜你通关完成*******\n");
    printf("谢谢使用本软件，再见！！");

    return 0;
}

int  jiafa()
{
    int n = 0,X = 0,Y = 0,k = 0,a;
    printf("开始加法练习:\n");
    for (k=0;k<=9;k++)
    {
        chuti();
        scanf("%d",&a);
    } /*加法练习*/
    return 0;
} 

看情况是课程设计的题，唉

switch(n)
{case 1: {printf("11+23=\n");break;}
case 2: {printf("15+22=\n");break;}
case 3: {printf("18+9=\n");break;}
case 4: {printf("38+29=\n");break;}
case 5: {printf("21+3=\n");break;}
case 6: {printf("44+51=\n");break;}
case 7: {printf("2+6=\n");break;}
case 8: {printf("43+98=\n");break;}
case 9: {printf("56+12=\n");break;}
case 10: {printf("88+12=\n");break;}
case 11: {printf("2+96=\n");break;}
case 12: {printf("1+99=\n");break;}
case 13: {printf("54+21=\n");break;}
case 14: {printf("11+2=\n");break;}
case 15: {printf("54+9=\n");break;}
case 16: {printf("32+19=\n");break;}
case 17: {printf("77+32=\n");break;}
case 18: {printf("15+76=\n");break;}
case 19: {printf("25+65=\n");break;}
case 20: {printf("42+32=\n");break;}
}
提个建议运算的数字也用随机不是更好

if后面的表达式中应该用关系运算符==，不能用赋值号=啊...