C calculator refuses to work when more than 1 “if” statements are added

I made a small C calculator earlier today, and I noticed it worked fine when the only operation it was able to do was addition, however when I tried to add subtraction, multiplication or division, it would simply not give an output, and I don’t know the reason for it as another calculator I had made before (although much simpler) was able to do a similar process fine.

I am very new to C and programming in general though (C is the first programming language I am just picking up) so it might just be my fault.

This is the code on my program for now:

int main()
{
    int x;
    int y;
    int z;
    char c;
    printf("Number calculator advanced\n");
    printf("please enter 2 digits\n");
    scanf("%d%c%d",&x,&c,&y);
    if (c == '+')
    {
        z = x += y;
        printf("%d\n",z);
    }
    if (c == '-')
    {
        z = x -= y;
        printf("%d\n",z);
    }
}

as you know, I was expecting it to scan for the user’s math equation, and when a ‘-‘ or a ‘+’ was used, it would subtract or add both numbers, as it does for addition when it’s the only "if" statement that is used
The result I end up getting though, is this:

Number calculator advanced
please insert 2 digits
[example input:]
5 + 2

Process returned 0 (0x0)   execution time: 19.943 s
press ENTER to continue

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