#include <stadio.h>
int main (void)
{
float sum=0.0,avg=0.0;
printf("请输入两个整数:");
scanf("%d\n%d\n",&a&b);
sum=a+b;
avg=sum/2;
printf("两个数的和为：%d\n",sum);
printf("两个数的平均数为%f\n",avg);
       return 0;
}

不看不知道你错了好几个地方
#include <stadio.h>     //<stdio.h>
int main (void)
{
float sum=0.0,avg=0.0;
int a,int b;// a,b没定义
printf("请输入两个整数:");
scanf("%d\n%d\n",&a&b);//scanf("%d\n%d\n",&a,&b);
sum=a+b;
avg=sum/2;
printf("两个数的和为：%d\n",sum);
printf("两个数的平均数为%f\n",avg);
       return 0;
}

很谢谢你！啵啵