Anything per something means that is a rate, so you will have a variable on that, such as x.
So $2 per movie, is interpreted as 2x
The $10 is a set price for a rental card, and will not change.
So a linear equation is interpreted as y = 2x + 10
Set x to 6 because you are renting that many movies.
y = 2(6) + 10
y = $22