This only works if X=x. So, if we make the first equation #1, and the second, #2, then we need to subtract #1-#2, so that we can eliminate 4y. So now we have -2x = -16, if we divide both sides by 2, we get -x = -8, and if we multiply each side by -, we get x = 8. Substituting this into #1, we get 8 - 4y = 4. Subtracting both sides by 8, we get -4y = -4. Dividing both sides by 4, we get -y = -1, and multiplying both sides by -, we get y = 1. Hope this helps! :D