Answer:
9x + (6 + 9x) =12
Explanation:
For a combined equation, you need to eliminate one of the variables. For this example I eliminated the y variable.
Lets look at this equation, (You can do this for either equation, I just picked this one):
-9x + y = 6
You have to separate the y variable from the rest. So you add -9x to both side to cancel out the -9x.
Resulting in:
y = 6 + 9x
Now that you have an equation for the y variable, use the substitution method to add your new equation to the other.
9x + y = 12, becomes: 9x + (6 + 9x) = 12
That is your combined equation for the system.