How do you write intervals of increase and decrease?

Combined megan and kelly worked 60 hours.kelly worked twice as many hours as megan.how many hours did they each worked?

Two cars which are 40 miles apart start moving simultaneously in the same direction with constant speeds. if the speed of the car which is behind is 56 mph and the speed of the other car is 48 mph, how many hours will it take for the car which is behind to catch up the car ahead of it?

I’m still confused on how to work the percentages