Answer: 105
----------------------------------------------------------------
Work Shown:
x = length of shorter piece, 3x = length of longer piece
x+3x = 140
4x = 140
4x/4 = 140/4
x = 35
3*x = 3*35 = 105
So the longer piece is 105 feet long (shorter piece is 35 ft).
Note how 35+105 = 140 which helps confirm the answer.