What is the value of a in the equation 3a + b = 54, when b = 9?

Asporting good store is offering 30 percent off of the original price(x) of football cleats. the discount will be reduced by an another $7 before sales tax.

Pls yall i really need the answer fr fr

Acommunity group is building a garden on a rectangular lot of land. the lot measures 5x by 10x and the garden will be circular with a radius of 3x. how much of the land will be left over after the garden is built? a. 41 pi x^2 b. x^2 (50 - 9 pi) c. x^2 (50 - 3 pi) d. 41x^2