I think I understand what you're asking, though it's rather hard to say.

Ok, so there's two parts.

1. You create set C from A and B

2. You check C against the sum of set B

Arrays are extremely useful here, and they're quite simple.

Code:

for(int n=0;n<5;n++)
{
cout << numbers[n] << endl;
}

That goes through numbers and couts the first, second, third, etc. If you don't understand that I would recommend taking a look at a tutorial on arrays, and basic C(++) language.

So, you go through c[0]+a[0]+b[0] to the end.

Now for the second part, you can go through your array of numbers in B adding them up.

Code:

for(int n=0;n<10;n++)
{
number += n;
}

The above adds up all the numbers between 0 and 9, I'm sure you can think of a way to modify that to use an array from before to find the sum of all the numbers in set B.

Then it's a case of go through each element in set C and check if sum_b <= c[n].