Use substitution to solve the system of equations.

y = −2x
x − 3y = 21

(3, 4)

(−6, 12)

(3, −6)

(−2, −6)

Respuesta :

The answer is (3,-6)
x-3*(-2x)=21
x+6x=21
7x=21
X=21/7
X=3
Now you substitute x=3 in the other equation
Y=-2*3
Y=-6