My brother needs help with this

Find and simplify an expression for the area of five rows of x squares with side lengths of x centimeters.

Put the equation in slope intercept form by solving for y

Acomputer store buys a computer system at a cost of $370.80. the selling price was first at $ 618, but then the store advertised a 20 % markdown on the system. answer parts a and b. a. find the current sale price.