The first side of a triangle is twice the length of the second side; the third side is 20 feet less than three times the second side. The perimeter of the triangle is 106 feet. Find the three sides.

Answer 1

F = 2S

T = 3S-20

F+S +T = 106

substitute 1st two equations into the 3rd equation

2S + S + 3S -20 = 106

6S = 126

S = 126/6 = 21

F=2S = 42

T = 3S-20 = 63-20 = 43

sides are 21, 42 and 43 feet