If x and y are positive integers, and 3x+2y=21, what is the sum of all possible values of x?

Question

hero · Answer

What is y when x = 1?

anonymous · Answer

9

hero · Answer

Do you know why we shouldn't start with x = 0?

anonymous · Answer

because it is not a positive integer

hero · Answer

Well, what about x = 2? Will that work for this?

anonymous · Answer

No?

hero · Answer

Why not?

anonymous · Answer

i couldnt find a number that works for both

hero · Answer

It's because if x = 2, then y won't be an integer.

anonymous · Answer

ya true

hero · Answer

So just continue from there until you collect all the possible x values that work, then add them up.

anonymous · Answer

ok thanks can you tell me the answer so I can check if I get the right answer

hero · Answer

It's better if you tell me what you think the answer is, then I'll let you know if it's correct or not.

anonymous · Answer

ok so is 9 the answer because 1+3+5?

anonymous · Answer

because 7 doesn't work because you would have to put 0 which is not a positive integer

hero · Answer

Congrats

anonymous · Answer

thanks!

hero · Answer

You're welcome