In a right triangle the length of the hypotenuse is 20 inches and the length of one leg is 15?

The length of the other leg would be 13.2. Keep in mind the Pythagorean theorem: a2 + b2 = c2 a would be the length of one side of the triangle, b is the other side, and c is the hypotenuse. a2 + (15)2 = (20)2 a2 + 225 = 400 a2 = 400 - 225 a2 = 175 √a2 = √175 a = 13.2