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 4 kilometers by car . what is the distance , in kilometers , from the dormitory to the city ?
"whole trip = distance by foot + distance by bus + distance by car x = 1 / 5 x + 2 / 3 x + 4 x - 13 / 15 x = 4 2 / 15 x = 4 = > so x = ( 15 / 2 ) * 4 = 30 km answer a"
multiply(4, inverse(subtract(1, add(divide(1, 5), divide(2, 3)))))