13 rides
First, deduct the price of the admission to the park from the $80.
$80.00 - $8.50 = $71.50
This is the amount she has left over to spend on rides.
Now, divide that amount by using the cost of the rides.
$71.50 ÷ $5.50 = 13 rides
This is the amount of rides she will be able to go on.