Question 961624
This is uniform work-rates type of problem.


Let r be rate of washing cars for 1 person in unit of car per hour.


RT=J  rate time job, and "job" means whatever amount of CARS.


{{{system(18r*4=50,22*r*t=48)}}}.
Note this system uses two unknown variables and is of two equations.  One of the equations has just the variable, r, and that is the equation you use first; and then substitute this into the other equation and finish solving for t.