If each small tile cost 15 pesos & each big tile should emmanuel use to economize in tilin his floor? explain why

It's not possible to answer this question without the other information in the middle,
which you skipped as you copied the question. That information tells us the size
of the big tiles, the size of the small tiles, and the size of the room.  That's how we
figure out how many tiles he needs, and once we know that, we can figure out how
much they cost.  (You also skipped the cost of the big tiles. We'll need that too.)