HELP NEEDED PLEASE !! WILL GIVE BRAINIEST What equation combines with the given equation to form a system of equations with the solution x = 3 and y = 9? x + 2y = 21

A. 4x + 6y = 64

B. 2x + y = 36

C. 4x + y = 21

D, 3x + 2y = 28

C

Step-by-step explanation:

x + 2y = 21

4x + y = 21

Multiply the second equation by -2 to get:

 -8x - 2y= -42  {Add this to the original equation; y's will be eliminated}

+  x + 2y = 21

-7x = -21

x = 3

see if y = 9 works . . .

3 + 2(9) = 21  and it does

30

step-by-step explanation:

idk

i hope i