Question 977827
You copied the problem incorrectly
You have more than 40 students 
17 students rode an airplane only, 28students rode boat only, 10students rode train only.
Then later you say "3students rode boat only"
so which is it 28 rode the boat only or 3 rode the boat only
first you say that 17 rode the plane only but you have 4 students who say they rode a plane