# How do you balance the equation SnO_2 + C -> Sn + CO?

You will see that $O$ is double at the left, so we have to double the $C O$ at the right. But then we also have to double the $C$ at the left, or the $C O$ won't come out right:
$S n {O}_{2} + 2 C \to S n + 2 C O$