This is a simple concept but it can be confusing. You were right when you put 10 next to 6 because you multiply 3 by 2 and also 5 by 2 to get 10. BELIEVE IN YOURSELF!!!! ;) For the other ones, you just divide whichever number is in the box by 3 or 5 (depending on which column it is) and multiply the other column by that answer and you should get the answer to fill the missing box. For example, 9 would be next to 15 and so on and so forth. Hopefully that whole paragraph helped!!!:)!