Answer:
71.63 kilowatts hours
Explanation:
We are told in the question:
John's electricity bill costs $20.90 per month plus $1.23 per kilowatt hour.
We are to find, How many kilowatt hours can he use and keep his monthly cost no more than $109.
Step 1
$109 - $20.90
= $88.1
$88.1 is the amount left to spend on killowatts of electricity per hour after removing the normal monthly electricity bill in a month
Step 2
$1.23 = 1kilowatts per hour
$88.1 = y kilowatts per hour
Cross Multiply
= $1.23 × y kilowatts per hour = $88.1 × 1 kilowatts per hour
y kilowatts per hour = $88.1 × 1 kilowatts per hour/ $1.23
= 71.62601626kilowatts hour.
Approximately = 71.63 kilowatts hour
Therefore, John can use 71.63 kilowatts per hour and keep his monthly cost no more than $109