The perimeter of an equilateral triangle is 6 cm more than the perimeter of a square. The length of a side of the square is 3 cm less than the length of a side of the equilateral triangle. Find the area of the square.

3t=4s+5 (s=side of square, t = side of triangle)

s=t-3, t=s+3, using this value for t in the first equation gives us:

3 (s+3) = 4s+5

3s+9=4s+5

-s=-4

s=4

so the side length of the square is 4cm and the area of a square is just s^2

A=16cm^2