Two people start walking at the same time in the same direction. one person walks at 4 mph and the other person walks at 7 mph. in how many hours will they be 2.25 miles apart?

Problem number 26 of the rhind papyrus says: find a quantity such that when it is added to of itself the result is a 15. the modern day equation that models this problem is x + x = 15. what is the solution to the equation? x = 10 x = 12 x = 15 x = 30