Jerry and his father are cleaning the house. Jerry can finish clean the house in 2 hours, his father can finish 0.5 hour faster than Jerry. How long would it take Jerry and his father to finish cleaning the house?
the father can do the job in 1.5 hours.
So, as with most of these work problems, if they can finish in x hours working together,
1/2 + 1/1.5 = 1/x
Now just solve for x.