Hello!
We can write an expression to show this scenario. Write this in the equation format y = mx + b:
m = rate of change, or cost per ride
b = initial cost, or cost to enter the fair
y = 2.50x + 4
Solve for the amount of rides possible with $21.50:
21.50 = 2.50x + 4
Subtract 4 from both sides to isolate x:
17.50 = 2.50x
Divide both sides by 2.50:
17.50/2.50 = 7 rides.