This is a fraction question obviously. The best trick not to make a mistake is to make a drawing.

You are told that you have 3" bolt with 1/4" head. It leaves 2 3/4" of "real bolt".

It goes through 1 1/2" of pine board, a 1/16" washer, and a 1/8" nut.

Common denominator is the key.

Bolt:

You substract to find

I may have made a mistake so I suggest you redo the calculations.

Don't hesitate to ask further questions.