The length in feet of three ropes are consecutive multiples of three. If each rope were 4 feet shorter, the sum of their lengths would be 42 feet. Find the lengths of the three ropes.
If the lengths are 3x-3,3x,3x+3, then
3x-7 + 3x-4 + 3x-1 = 42
x = 6
The ropes are 15,18,21