Answer:
36 ft
Explanation:
The ratio of the lengths of the sides is the same as the ratio of the perimeters.
Just like one side (15 ft) of triangle ABC is 3 times as long as the corresponding side (5 ft) of triangle DEF, the perimeter of triangle ABC is also 3 times the perimeter of triangle DEF.
15/5 = x/12
3 = x/12
x = 36
Answer: 36 ft