So, their are 120 students (irrelevant) 78 rode the LRT (irrelevant) 68 rode the bus (relevant) 20 rode the bus and Jeep (relevant) 19 rode the jeep and LRT (irrelevant) 15 rode all three (relevant) So; Out of the 68, 35 rode on something else>>to get the answer you would take 35 away from 68 and get 33 Hope this helped...