Explanation:
x = number of visits
y = number of earned points
the equation for the situation is (remember the 20 points starting balance) :
y = 5.5 × x + 20
and the question is now actually after how many visits she reached 75 earned points.
therefore,
75 = 5.5 × x + 20
55 = 5.5 × x
x = 55/5.5 = 10
she gets a free movie ticket after 10 visits.