a. The electric oven will function normally if the voltage varies from 220 volts by 10 volts

Thus if the voltage of an oven is x then it will function normally if the difference between its voltage x and 220 volts is less than or equal to 10. The difference can be positive or negative

Therefore write the absolute value inequality as:

Therefore write the absolute value inequality that gives the voltage x for which the oven will work normally