Use the substitution method to solve the system of equations. Choose the

correct ordered pair.

y = 10x - 9

y = x + 18

A. (1,1)

B. (2,11)

C. (3,21)

D. (4, 31)

Answer: C. (3,21) - x = 3; y = 21

Step-by-step explanation:

y = 10x - 9. (-1)

y = x + 18

-y = - 10x + 9

y = x + 18

-9x + 27

x = 27

-9

x = 3

y = x + 18

y = 3 + 18

y = 21

C. (3,21)

Step-by-step explanation:

multiply the 2nd equation by - 10 to cancel out the x.

y = 10x - 9

-10 (y = x + 18)

y = 10x - 9

-10y = - 10x - 180

-9y = - 189

y = 21

Now plug y = 21 into either original equation.

y = x + 18

21 = x + 18

Take 18 from each side.

3 = x

Answer: (3, 21)