#include<stdio.h>
int main(void)
{
    int dogs;
    printf("How many dogs do you have?\n");
    scanf("%d",&dogs);
    printf("So you have %d dog(s)!\n",dogs);
    return o;
}

return 0，不是return o！！！

为使输出结果好看，最好把printf("So you have %d dog(s)!\n",dogs);里的括号也去去掉吧，还有就是2楼说的问题，楼主一定要细心啊！