Why are basic facts needed when dividing large numbers?

Which represents the solution set of the inequality 5x-9 < 21? a. x < 12/5 b. x > 12/5 c. x > 6 d. x < 6

I'm confused on this could anyone me and show me what i need to do to solve it.

The art class is planning to paint a mural on an outside wall. this figure is a scale drawing of the wall. width: 11 in length: 28 in unit rate: 1.5 ft per in. write the ratio of the area of the drawing to the area of the actual mural. write your answer as a unit rate. show that this unit rate is equal to the square of the unit rate 1.5 ft per in