Solve systems by substitution

(1/6) x - (1/12) y = - (1/2)

and

-2x + y = 6

This is a trick question, because the two equations are linearly dependent. If you multiply the top one by - 12, you get the bottom one. This means that essentially, the same equation is written twice, so you don't have enough information to solve for x and y.

So at most you can drop one of the equations, and you are stuck with the other one.