For his long distance phone service, Keith pays a $3 monthly fee plus 11 cents per minute. Last month, Keith's long distance bill was $13.67. For how many
minutes was Keith billed?

He was billed for 97 minutes.

Step-by-step explanation:

Knowing that Keith's plan has a $3 base fee and takes 11 cents per minute, we  can start by removing the $3 from the equation since we are looking for the amount of minutes he was billed for.

$3 + $0.11x = $13.67 ---> $3 (-$3) + $0.11x = $13.67 (-$3)

---> $0.11x = $10.67

Next, divide both sides by 0.11.

$0.11x = $10.67 ---> $0.11x ÷(0.11) = $10.67 ÷(0.11) ---> x=97

Keith used his long distance phone service for 97 minutes.