7.9 - 4.012. i really don't know the answer

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36

50 plz, given the system of equations, match the following items. x + 3 y = 5 x - 3 y = -1 a) x-determinant b) y-determinant c) system determinant match the following to the pictures below.

Set up and solve a proportion for the following application problem. if 55 pounds of grass seed cover 404 square feet, how many pounds are needed for 7272 square feet?