One pipe can fill a tank in 20 minutes. A second pipe can fill the tank in 30 minutes. If the tank is empty, how long would be required for the two pipes operating together to fill it?
I need the rate of work (R), the time of work (T) , and the work done (W)
the equation is RT = W.
It would help if I am provided a detailed explanation

(It might also have helped immensely if you had been listening when this was being explained in class.)The first pipe fills 1/20 of the tank each minute.The second pipe fills 1/30 of the tank each minute.Operating together, the two pipes fill ( 1/20 + 1/30 ) of the tank each minute.In order to add these fractions (or any fractions), you need a common denominator.For these particular ones, ' 60 ' is a good choice.( 1/20 + 1/30 ) = ( 3/60 + 2/60) = 5/60 = 1/12The rate of work is 1/12 tankful per minute .The most sensible choice for the time is 12 minutes.R x T = W( 1/12 tankful per minute ) x ( 12 minutes ) = 1 full tank