Answer:
Area = 180 cm^2
Explanation:
See attached image. The width of the rectangle, a , is the hypotenuse of a right triangle with legs 15 and 20.
Use the Pythagorean Theorem: leg^2 +leg^2 = hypotenuse^2
The width, w, is one leg of a right triangle that has hypotenuse 20 and one leg 16.
The rectangle has length 15 cm and width 12 cm so its area is 12 x 15 = 180 cm^2