Answer:
225

Explanation:
First, find the perimeter of the triangle. We will use the Pythagorean Theorem to find the length of the hypotenuse of the triangle.
+
=

+
=

400 + 225 =

625 =

=

25 = c
The perimeter of the triangle is: 25 + 20 + 15 = 60
The perimeter of the square is the same (60), so the length of each side is 15 (60/4).
To find the area of a square you multiply the length times the width, or in this case, 15 x 15 which is 225.
Helping in the name of Jesus.