Question

A reel of electric wire 150 metres long cut into two pieces. One is 40 metres shorter than twice the length of the other. How long is each piece.

Answer 1

Let one be x metres long
then the other is 150 - x

x+40 = 2(150-x)
x+40 = 300 - 2x
3x = 260
x = 260/3 m

one is 260/3 m, the other is 150-260/3 or 190/3 m
or in decimals, appr 86.67 m and 63.33 m.

check:
one is 86.67
twice the other is 126.67
which is 40 m more

Answer 2

Or, you can work it from the other side, which I find easier at the start:

x + 2x-40 = 150
3x = 190
x = 63.33
2x-40 = 126.67-40 = 86.67