There are 25 tiles total - triangles or squares - 84 edges
triangle (t) = 3 sides
square (s) = 4 sides
t+s= total tiles
t+s = 25 ← solve
3t + 4s = total sides
3t + 4s = 84 ← solve
t = 16 s = 9
Check
16 + 9 = 25
3(16) + 4(9) = 84
48 + 36 = 84
There are 9 square tiles in the box
