Every point is C has a pre-image in B and that pre-image has itself a pre-image in A.
Hey I'm in need of a push in the right direction.
My problem is:
Assume A,B,C are arbitrary sets show if f:A -> B is onto and g: B->C is onto then g(f): A->C is onto. (EDIT - meant to say g(f))
What do I need to show to prove A-C is onto?