The independent variable is a constant that does not rely on anything. This will be $5 because she has to pay it every month regardless.
The dependent variable change and affect the outcome. This will be $1.50. She has to pay per movie. If she doesn't watch a movie she doesn't pay anything on top of the $5. If she watches 10 movies, she payed $15 on top of the $5.
The equation:
x = Number of movies.
y = price
y = 5 + 1.5x
Table:
y x
11 4
12.5 5
14 6
15.5 7
17 8
18.5 9
20 10
