In traveling from a dormitory to a certain city, a student went 1/5 of the way by foot, 2/3 of the way by bus, and the remaining 12 kilometers by car. What is the distance, in kilometers, from the dormitory to the city? Answers:
A) 30  B) 45  C) 60  D) 90  E) 120

Rationale: whole trip = distance by foot + distance by bus + distance by car x = 1 / 5 x + 2 / 3 x + 12 x - 13 / 15 x = 12 2 / 15 x = 12 = > so x = ( 15 / 2 ) * 12 = 90 km answer d
Answer: D