Question

number of bubble teas | 1 | 2 | 3
total cost ($) | 4 | 8 | 12
total cost = 4 · number of bubble teas
a rule tells you what to do with the starting value, or input, to get the final value, or output.
what is the starting value, or input?
the number of bubble teas.
what is the final value, or output?
the number of bubble teas
the total cost

Explanation:

To determine the final value (output), we refer to the rule and the table. The input is the number of bubble teas, and the output is what we get after applying the rule (multiplying input by 4). The total cost is the result of the calculation, so it's the output. The number of bubble teas is the input, not the output.

Answer:

the total cost