A. 100 = 50 + 15x
50 = 15x
3.33 = x
He can go 3 times, with 5$ remaining.
B. 100 = 25x
4 = x
He can go 4 times on normal admission.
C. 160 = 50 + 15x
110 = 15x
7.33 = x
He can go 7 times, with 5$ remaining.
D. 160 = 25x
6.4 = x
He can go 6 times, with 10$ remaining.