Which representation of a transformation on a coordinate grid does not preserve congruence?

Which value of c would make he following expression completely factored? 8x+cy

Evaluate the expression for the given value of the variable 7a - 4a for a =8

To solve the system of equations below, grace isolated the variable y in the first equation and then substituted into the second equation. what was the resulting equation? 3y=12x x^2/4+y^2/9=1