Answer
a. acceptable.
b. not acceptable.
Work Step by Step
The formula that describes the acceptable voltage is
$$ |x-220|\leq 8$$
We plug in the given voltage values and if the inequality proves true, then the voltage is acceptable.
a. Since $|214-220|=6\le 8$, then the voltage of $214$ Volts is acceptable.
a. Since $|209-220|=11\gt 8$, then the voltage of $209$ Volts is not acceptable.