A chef can make 12 omelets in one our. what is the rate of omelets per minute?

Set up your equation to cancel out units you don't want and introduce units that you do ...

(12o/hr) (hr/60min) = 0.2o/min

So the chef can make 1/5 of an omelet per minute

There are 60 minutes in one hour, so you would divide 12 by 60

they make 0.2 omelettes a minute