Variable $m$ cannot be equal to $0$ since division by zero is not defined. Multiply both sides of the equation by $100m$, the least common multiple of $m,100$.
$$100\times 12=m\times 12$$
Multiply $100$ and $12$ to get $1200$.
$$1200=m\times 12$$
Swap sides so that all variable terms are on the left hand side.
