Question

I need help with these 2 problems

Answer 1

The formula for the area of a rectangle is
`b\cdot h`, so given that
`h=5x+3, b=3x-4`, the area of the entire rectangle is
`(3x-4)(5x+3)=15x^2-20x+9x-12=15x^2-11x-12.`. We now subtract the white part, with area
`2x*4x=8x^2`, so
`15x^2-11x-12-8x^2=7x^2-11x-12`