SOLUTION: Tom and dick working together can perform a task in 2 hours and 24 minutes. Dick and harry working together can perform the same task in 3 hours and 36 minutes. If dick works alone

Let T be the rate of Tom  (i.e. the part of the job he makes in each hour).

Let D be the rate of work for Dick, and

let H be the rate of work for Harry.


Then we have these two equations

    T + D =  =     (1)   (here    represents  2  hours = 2 hours and 24 minutes)

    H + D =  =     (2)   (here    represents  3  hours = 3 hours and 36 minutes)


Adding these equations, you get

   T + H + 2D =  +  =  +  = .    (3)


We also know that the rate of work for Dick is    of the job per hour.


Hence, from (3) we have

    T + H +  = ,  or

    T + H =  -  =  -  = .


It means that Tom and Harry will complete the job in  hours = 2  hours = 2 hours 46 minutes and 9 seconds (rounded).    ANSWER