Solve each system using elimination
x-3y=27
3x-3y=39

Divide the problem into 3 steps. 1.Eliminate one variable. 2. Solve for the remaining variable. 3. Use that information to solve for the second variable.
1.
Multiply the top equation by -3
-3x+9y=-81
3x-3y=39
If you add these two equations together, you are left with
6y=-42
2.
Solve for y by dividing both sides by 6
y=-7
3.
Plug -7 in for y in the either equation. I'll use the top one. It's just simpler.
x-3(-7)=27
x=6

Check your work plugging both variables into both equations to see if they are still true.