My 9th grade son had this math problem, which seemed unsolvable to me:
$$2x - 2y = 11$$ $$x = y - 2$$
So we can use substitution to come up with: $$2(y - 2) - 2y = 11$$
Now distribute: $$2y - 4 - 2y = 11$$
Reduce $2y$ and $-2y$ cancel each other out
Answer $$-4 = 11$$
Did we do something wrong here, or is this math problem unsolvable?