The perimeter of the original triangle is 48 inches. what is the perimeter of the reduced triangle? ((the answer that i put in is incorrect, but i want to know the right answer & how to solve it))

The length of the hypotenuse equals to the square root of the sum of the square of the other two sides.
12x12+16x16=144+256=400
The square root of 400 is 20.

By the same way, you can find the length of the hypotenuse of the reduced triangle
9x9+12x12=81+144=225
The square root of 225 is 15
The length of the hypotenuse is 15

The perimeter =12+9+15
The perimeter=36