You get 36 if you multiply 4 by 9. the factor of four are 2 and 2. The factors of 9 are 3 and 3.

You get 42 if you multiply 6 by 7. 2 and 3 are factors of 6, and 7 doesn't really have factors, unless you count 1 and 7.

You get 56 if you multiply 7 by 8. 2 and 4 are factors of 8, and 7 again does not have factors, unless you count 1 and 7.

Sorry if I was late.

And no, I didn't google it, I know it off the top of my head. I'm good at Math.