2483 dividido 9 ayuda plis (help plis)

Me find the missing dimension of a triangle height: 7 in., area: 21^2

Brook states that the distance on the line is 4 units. caleb states that the whole line does not have a distance because it continues on forever. vivian states that the line is 6 units long. which distance did brook measure? which distance did vivian measure?

How do you do the foil method with polynomials?