Use the distributive property to solve 6*35

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

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?

I’ve been trying all day to figure this puzzle out. i need the work for it aswell. it is a factoring polynomials tarsia. the image is below.