In traveling from a dormitory to a certain city, a student went 1/3 of the way by foot, 1/4 of the way by bus, and the remaining 5 kilometers by car. What is the distance, in kilometers, from the dormitory to the city? Choose the correct answer
A) 13 B) 17 C) 42 D) 15 E) 12

Rationale: "whole trip = distance by foot + distance by bus + distance by car x = 1 / 2 x + 3 / 5 x + 5 x - 1 / 2 x - 3 / 5 x = 5 x = 12 km option : e"
Answer: E