Answer:
You bought 15 tickets
Explanation
You want the equation to be equal to 11.50. Per person it's 4 dollars so you add 4 each time. The amount it costs for each ride ticket is .5 and you want to go on multiple rides so you'd add a variable to .5 and set the equation to
0.50n + 4 = 11.50 which gives you 15 tickets.