To find the monthly change in Devon's account after paying for the internet service, we start by determining the monthly payment.
Devon made a total payment of $936 over 8 months. To find the monthly payment:
\[ \text{Monthly Payment} = \frac{\text{Total Payment}}{\text{Number of Months}} = \frac{936}{8} = 117 \]
This means Devon pays $117 each month for internet service. Since this is a payment, it results in a decrease in his account balance.
Therefore, the change in Devon’s account each month after paying for the service is:
\(-117\)
The correct answer is:
-$117