Answer:
(x, y) = (-3, -6)
Explanation:
You want the solution to the system of equations 6 = -4x +y, -5x -y = -21 using the substitution method.
Expression for y
Adding 4x to the first equation gives an expression for y:
6 +4x = y
Substitution
This can be substituted into the second equation:
-5x -(6 +4x) = 21
-9x -6 = 21 . . . . . simplify
-9x = 27 . . . . . . . add 6
x = -3 . . . . . . . . . divide by -9
6 +4(-3) = y . . . . . . . find y using the expression for y
6 -12 = -6 = y
The solution is (x, y) = (-3, -6).