Answer: 9 inches.
Do the pythagorean theorem to find your answer.
Formula: a^2 + b^2 = c2
12 = b
15 = c
a^2 + 12^2 = 15^2
Simplify the equation
a^2 + 144 = 225
Subtract 144 on both sides.
a^2 = 81
Square root of 81 is 9.
Answer: To find the area of a rectangle, multiply its height by its width. For a square you only need to find the length of one of the sides (as each side is the same length) and then multiply this by itself to find the area.