Answer:
A) 
B) $1200
Step-by-step explanation:
Let w represent employee's weekly sales and
be total weekly earnings.
We have been given that a phone store employee earns a salary of $450 per week plus 10% commission on her weekly sales.
A) The total weekly earnings of employee would be weekly salary plus 10% of weekly sales.
10% of weekly sales, w, would be 

Therefore, the function
models the employee's weekly earnings.
B) To find the weekly sales in the week, when employee earned $570, we will substitute
in our formula and solve for w as:






Therefore, the amount of employee's weekly sales was $1200.