Question

Marty ate 1/4 of his pizza and Luis ate 1/3 of his pizza. Marty ate more pizza than Luis. Is that possible?

Answer 1

Yes, it is possible depending of the size of their pizza.

Answer 2

Of course.

You can only say for sure that 1/4 of a whole thing is less than 1/3 of a whole thing
if the whole things are equal size.

If Marty's pizza was 1/3 bigger than Luis' pizza, then they both ate the same amount.
If Marty's was MORE than 1/3 bigger than Luis', then Marty ate more pizza.