EXPLANATION
Let's see the facts:
Admission fee = 6 dollars
ride cost = $0.75
Let's call x to the number of rides.
We have 15 dollars, so the relationship is as follows:
15 = 6 + 0.75x
Subtracting -6 to both sides:
15 - 6 = 0.75x
Simplifying:
9 = 0.75x
Dividing both sides by 0.75:
9/0.75 = x
Simplifying:
12 = x
Switching sides:
x = 12
Answer: I can go on 12 rides.