Call the length of the first piece, L, the second, 2L, and the third 3L
So we have
L + 2L + 3L = 36
6L = 36 divide both sides by 6
L = 6 that's the length of the first piece
2L = 2(6) = 12 and that's the length of the second piece
3L = 3(6) = 18 and that's the length of the third piece
