A factory is currently running at $85\%$ of its original capacity, and management is considering upgrading the equipment. The upgrade will take $6$ months, during which time the factory will not run at all. Once complete, the factory’s output will increase to $120\%$ of the original capacity.
After how long would the upgraded factory’s production match the current $85\%$ production? In other words, how long will it take for the factory to make up for the loss of $6$ months?
This what I have come up with so far:
$0.85E - 6m = 100$ and $1.20E + 6m = m$
$E$ represents the percentage capacity, $m$ represents the months, and $100$ represents the factory original output of $100$ units per month.
I understand how to solve using system of equations but I am having difficult with coming up with a set of equations for this problem in particular.