Jess ate 1/4 of a pizza.Jack ate 1/3 of the same pizza.Dennis ate 1/2 of the same pizza.Explain and show with math if this is possible?

Answer 1

The pizza is cut into 12 slices.

Jess ate 3 slices (1/4 = 3/12).
Jack ate 4 slices (1/3 = 4/12).
Dennis ate 6 slices (1/2 = 6/12).

Add: 3+4+6 = ??

Answer 2

1/4 + 1/3 + 1/2 = 3/12 + 4/12 + 6/12 = 13/12 = 1 1/12. Impossible, because 13/12 is more than a whole pizza.