Systems of equations

Two equations, two letters. First get down to one equation with one letter.

Look at the y terms: 12y in the first and −12y in the second. They are opposites, so adding the two equations makes them cancel.

Add left to left and right to right — both sides stay equal. That gives 8x = 40.

One letter left. 40 ÷ 8 = 5, so x = 5.

Now put x back into either equation to find y: y = −1, so the solution is (5, −1).