Hi im learning for a exam in Theoretical computer science. And im learning with the exams of the last years because the task setting is very similar every year. And now i can solve almost all of this tasks except of one: There is always one Question about the "p vs. np" Problem.

An example of the lat year:

We have given the "Tile Cover" Problem witch says:
We have a "big" rectangle with a page length of 
n x m ∈ N
and we have k "small" rectangles ("tiles") r1, r2, ..., rk 

The Question is if all the "small" rectangles fit in the "big" one without leaving any space on it.

And now ther are some tasks for this Problem and i already despair on the first one witch says:

"Justify informal why the 'Tile Cover' problem is in NP"

How to solve this Problem, or a similar one (bacause i dont think it will be the same in this year)