Does the graph below represent a function?

STEP 1:
find the total number of cars in the parking lot when it's full

= 6 rows * 12 cars per row
= 72 cars in full lot

STEP 2:
subtract 15 cars from number in full lot (step 1 answer)

= 72 - 15
= 57 cars left

ANSWER: There are 57 cars left in parking lot an hour later

Hope this helps! :)