got the answer accepted:
#include <iostream>
using namespace std;
int main() {
long int n,a,b,c=0,rev1=0,rev2=0,rev3=0,rem1,rem2,rem3;
cin>>n;
while(n--){
cin>>a>>b;
rev1 = 0;
rev2 = 0;
rev3=0;
c=0;
while(a>0){
rem1 = a%10;
rev1 = rev1*10 + rem1;
a = a/10;
}
while(b>0){
rem2 = b%10;
rev2 = rev2*10 + rem2;
b = b/10;
}
c = rev1+rev2;
while(c>0){
rem3 = c%10;
rev3 = rev3*10 + rem3;
c = c/10;
}
cout<<rev3<<'\n';
}
return 0;
}