Question

How can I tell input from output?
Dollars Spent: 10, 11, 9, 10, 13, 5, 8, 4
Gallons Bought: 6.3, 6.1, 5.6, 5.5, 8.3, 2.9, 5.2, 2.7

Gallons bought seems like the logical answer, but dollars is the x value. Which would I pick?

Answer 1

You spend x dollars (the input) and you get y gallons (the output).