Answer:
Isaac earned $117.99 this week
Step-by-step explanation:
Percentages
The N% of a quantity M is calculated as follows:
N * M / 100
Isaac earns a 9% commission for his sales.
This week he sold $1,311, thus his commission is:
9 * 1,311 / 100 = 117.99
Isaac earned $117.99 this week