Is this the correct algebraic expression for r-9, 9 fewer than r

Scarlet bought three pairs of sunglasses and two shirts for $81 and paula bought one pair of sunglasses and five shirts for $105 what is the cost of one pair of sunglasses and one shirt?

Geometry in the diagram, ∠abc is a right angle. ∠dbc = 30°27'40". find the measure of ∠abd.

If you prove that ∆wxz is congruent to ∆yzx, which general statement best describes what you have proved?