We can multiply the top equation by 3 and the multiply the bottom equation by -1.

When we multiply the top by 3 and the bottom by -1 we get

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these new equations. Now, we can cancel out the 6x and the -6x, the 3y and -3y, and even the 12 and the -12.

When we cancel out the variables, and the constants, we get the solution 0 = 0. This means that there are infinitely many solutions. There is no need to plug this back into either of the original equations.

Since we get 0 = 0, our solution is infinitely many solutions.