You ride the roller coaster 8 times.
Explanation:
Step 1; You need 4 tickets to ride the Ferris wheel and 8 tickets to ride the roller coaster. You have been on the Ferris wheel 26 times.
Tickets needed to ride Ferris wheel = 4 tickets,
Tickets needed to ride the roller coaster = 8 tickets.
Tickets spent riding the Ferris wheel = tickets to ride the Ferris wheel × Number of times on the Ferris wheel = 8 tickets × 26 times = 104 tickets.
Step 2; We need to calculate the number of remaining tickets and how many times I can ride the roller coaster.
Remaining tickets = 168 - 104 = 64 tickets.
Times I can ride the roller coaster = remaining tickets / tickets to ride the roller coaster
= 64 / 8 = 8 times.