Algebra
posted by Anonymous .
The lengths in feet of three ropes are consecutive multiples of three. If each rope were four feet shorter, the sum of their lengths would be 42 feet. Find the lengths of the three ropes.

let the length be x3, x, and x+3
had each been 4 ft shorter, they would have been:
x7, x4, and x1
x7 + x4 + x1 = 42
3x = 54
x = 18
the ropes are 15, 18 and 21 ft each