Question

two lengths of stereo wire total 32.5 ft. one length is 2.9ft longer than the other. how long is each length of wire?

Answer 1

The length of the long one is half the total plus half the difference:
(1/2)(32.5 +2.9) ft = 17.7 ft

The length of the short one is 2.9 ft less:
17.7 ft -2.9 ft = 14.8 ft.

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If you like, you can write an equation for the length of the long wire (L).
L +(L -2.9) = 32.5 . . . . . . . total length of both wires
2L = 32.5 +2.9 . . . . . . . . . simplify, add 2.9
L = (1/2)(32.5 +2.9) . . . . . looks a lot like the solution above.