Answer:
C. Each calculator costs $80.
Step-by-step explanation:
Linear equation:
Has the following format:
[tex]y = mx + b[/tex]
In which m is the slope, and the meaning is how much the output changes when the input changes by 1 unit.
In this question:
Amount remaining after buying x calculators:
[tex]y = 1000 - 80x[/tex]
So the slope of -80 means that each calculator costs $80, since after buying a calculator, 80 is retired from the amount.
The answer is given by option C.