If i cut 4.75foot lengths of twine from a 240 foot spool of twine and i need to cut 42would 40.5 feet of twine be left?

Yes.
To do this, I turned it into an equation:  42 x 4.75 = 240 - 40.5
If the sides didn't turn out equal (for example, 2=3), then the answer would be no.
But since both sides ended up being 199.5, the answer would be yes.

Hope this helped, and feel free to ask more questions! (: