Ann cleans an apartment in 12 hours and liz cleans an apportment in 18 hours. how long would it take to clean an appartment together?

If Ann cleans in 12 hours then she cleans of the apartment per hour. Similarly Liz cleans of the appartment per hour. So together then can clean of the apartment for hour. Therefor it will take them hours to clean.

The general formula can be used as a check if needed.