Answer:
36 ft.
Explanation:
The given perimeter of triangle EDF is 12, in which the hypotenuse is 5. This means that it is a 3-4-5 triangle, meaning that ED = 3, DF = 4, EF = 5.
It is given that BC (the other triangle's hypotenuse) is 15. This means that the left triangle is to the scale factor of 3 of triangle EDF. Therefore, multiply 3 to all sides measurements, and then add all the sides to get the perimeter.
Hypotenuse: 5 x 3 = 15
Leg 1: 4 x 3 = 12
Leg 2: 3 x 3 = 9
Perimeter: 15 + 12 + 9 = 36
36 ft. is your answer.