The measure of the supplementary of an angle exceeds 3 times the measure of hte comp. of the angle by 10.?

supp = 3*comp + 10
comp=40

Setting up the equation:
supp = 3*comp + 10

But supp is by definition 90 degrees plus comp. Hence,
comp + 90 = 3*comp + 10

Grind through the algebra, and you should get comp=40.