30 POINTS !! HELP ME PLEASE! WILL GIVE BRAINLIEST TO BEST ANSWER SHOW STEPS PLEASE! THANK YOU SOO MUCH!

Solve the system of equations

{3x−y=6
{6x+y=21

The easiest way to solve this is by elimination.  

3x - y = 6  

6x + y = 21

Since you have a negative and positive y with the same coefficients (1), they cancel, and you add the other terms so it would look like:

9x = 27  

Then solving for x leaves you with x = 3  

Then you take the x value of three and plug it into to either of the equations, so  

3(3) - y = 6

9 - y = 6  

subtracting 9  

-y = -3  

then dividing by -1  

y = 3  

so the solution is x = 3 y = 3 or (3,3)  

Step-by-step explanation:

my answer is$ 12

step-by-step explanation:

because 15 -2=12

you can't solve x because it is 2 linear equation and you only have one equation