Let X be the number of students.
The total amount paid by them for the use of the boat will be 10X.
Now, if there were 3 more students, the number of students would be (X+3).
So, the total amount paid by them for the use of the boat would be 8(X+3).
The former and the latter amount being equal, then it ensues that 10X=8X+24..
Solve for X..