AMC 10 2015a Problem 2

A box contains a collection of triangular and square tiles. There are 25 tiles in the box, containing 84 edges total. How many square tiles are there in the box? $\textbf{(A) }3 \textbf{(B) }5 \textbf{(C) }7 \textbf{(D) }9 \textbf{(E) }\text{11}$