If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to x from the second equation is substituted into the first equation. 3x + 2y = -21 x - 3y = 4 (5 points) 3(3y + 4) + 2y = -21 3(-3y + 4) + 2y = -21 3x + 2(3y + 4) = -21 3x + 2(-3y + 4) = -21