Question

3x+3y=27 x-3y=-11

Answer 1

The best method to use here is probably elimination. You can solve this by just adding the two equations together. Add the left of the first to the left of the second, and add the right of the first to the right of the second.
\[(3x + 3y) + (x - 3y) = 27 + -11\]
See how one 3y is positive and one is negative? That will make y go away.
\[4x = 16\]
After that, it's easy to solve for x, and you can substitute back into either equation to get y.