Answer:
First, let's define some variables.
x = # of cell phones sold.
y = total weekly income.
y = $5.25x + $80
Another way is
If $80 is her standard income per week, then there is no variation in how much she's earning for that chunk of money. The phones however are $5.25 per phone shes sold, and that exact number could vary, so we’d represent that with “x.” the correct equation to solve this would be y(total weekly income)= $5.25x + 80