. David earned a fixed salary each month. In January, he spent $400 and
saved the rest. In February, he spent 10% more and his savings dropped by
20%. What was David's savings in January?

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?