C++ while to recognize when ive multiplied using addition

[jay123swe]

Hi guys.
I am currently working as a HTMLcoder for a company here in Sweden and I thought it would be great to learn some software development too so I bought myself a book reg. c++.
However there is something I've not been able to solve yet.
It's one of the questions in the book and this is how it should be done.

I will input two numbers (let's say 3 and 5) and that's no problem.
Then I should use addition using a (while?) loop to make it 3+3+3 etc. until it reaches 15 and then it should print $sum, however this has me wondering.
If I define x/y integers then should I add a sum integer too?
I believe that I in some way need to make the condition while (sum=x*y) .... if sum=xy cout sum?
But I cant get this to work with the integers x,y,sum where am I thinking wrong?
What approach should I take to solve it?

Thanks and sorry if anything's unclear just ask.

[Banfa]

Are you familiar with the concept of multiplication as repeated addition. For a sum y = a x b you can add b to itself a times or add a to itself b times.

Coding this you need to use a loop (personally I would use for) that for b iterations adds a onto the sum.