In a class of 40 students,17 have ridden an airplane,28 have ridden a boat,10 have ridden a train,12 have ridden both airplane and boat.3 have ridden a train only 4 have ridden an airplane only.some students in the class have not ridden any of these 3 modes of transportation and an equal number have taken all 3.

how many students have used all the 3 modes of transportation?



Train= 2
boat= 13
train= 10
1 5 1