Time Spent by Ben while cleaning his room=1 hour
⇒ Time Spent by Ben's Sister while cleaning his room=3×1 hour=3 hour--------------[As, it is given that, Ben's sister spent 3 times as many hours that ben spent while cleaning her room].
⇒Total Number of Hours that Ben and his sister spend cleaning their rooms altogether
=1 Hour +3 Hour
=4 Hour
→First,we have evaluated , the time spend by ben's sister while cleaning her Room.