y the ans is not 120?

Question

#include <iostream>
using namespace std;

int myFunc(int x) {
int m = x+100;
return m;
}

int main() {
int var = 20;
myFunc(var);
cout << var<<endl;
}

Answer 1

cuz you are printing var value that is 20..
calling of a function was at the wrong place
try this now
#include <iostream>
using namespace std;

int myFunc(int x) {
x = x+100;
return x;
}

int main() {
int var = 20;
cout << myFunc(var)<<endl;
}