c++报错如图片所示这怎么改呐

Question

#include <stdlib.h>
#include <string.h>
#include <math.h>
#define _CRT_SECURE_NO_WARNINGS

void ArithmeticMenu() {       //排序子菜单 数学求四则运算
    
    printf("*****************************\n");
    printf("*\t\t1.加法\t\t*\n");
    printf("*\t\t2.减法\t\t*\n");
    printf("*\t\t3.乘法\t\t*\n");
    printf("*\t\t4.除法\t\t*\n");
    
    printf("******************************\n");
}

void Arithmetic() {
    double x, double y;
    int choice;
    printf("请输入您的选择：\n");
    scanf_s("%d", &choice);
    switch (choice) {
    case 1:printf("请输入要算的数字：\n");
        scanf_s("%lf+%lf", &x, &y);
        printf("x+y=%lf\n", x + y);
        break;
    case 2:printf("请输入要算的数字：\n");
        scanf_s("%lf-%lf", &x, &y);
        printf("x-y=%lf\n", x - y);
        break;
    case 3:printf("请输入要算的数字：\n");
        scanf_s("%lf*%lf", &x, &y);
        printf("x*y=%lf\n", x * y);
        break;
    case 4:printf("请输入要算的数字：\n");
        scanf_s("%lf %lf", &x, &y);
        printf("x/y=%lf\n", x / y);
        break;
    
    default:printf("请重新输入\n");
        break;
    }

}

int main()
{

    ArithmeticMenu();

    Arithmetic();
    return 0;

}

Answer 1

#include <stdio.h>你都没加啊
double x,y;

修改如下：

 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define _CRT_SECURE_NO_WARNINGS
 
void ArithmeticMenu() {       //排序子菜单 数学求四则运算
    
    printf("*****************************\n");
    printf("*\t\t1.加法\t\t*\n");
    printf("*\t\t2.减法\t\t*\n");
    printf("*\t\t3.乘法\t\t*\n");
    printf("*\t\t4.除法\t\t*\n");
    
    printf("******************************\n");
}
 
void Arithmetic() {
    double x, y;
    int choice;
    printf("请输入您的选择：\n");
    scanf_s("%d", &choice);
    switch (choice) {
    case 1:printf("请输入要算的数字：\n");
        scanf_s("%lf+%lf", &x, &y);
        printf("x+y=%lf\n", x + y);
        break;
    case 2:printf("请输入要算的数字：\n");
        scanf_s("%lf-%lf", &x, &y);
        printf("x-y=%lf\n", x - y);
        break;
    case 3:printf("请输入要算的数字：\n");
        scanf_s("%lf*%lf", &x, &y);
        printf("x*y=%lf\n", x * y);
        break;
    case 4:printf("请输入要算的数字：\n");
        scanf_s("%lf/%lf", &x, &y);
        printf("x/y=%lf\n", x / y);
        break;
    
    default:printf("请重新输入\n");
        break;
    }
    system("pause");
}
 
int main()
{
 
    ArithmeticMenu();
 
    Arithmetic();
    system("pause");
    return 0;
 
}