For this case, the first thing we must do is define variables:
x: rolls of wrapping paper in one week
We now write the equation that models the profit of the band.
We have then:
P (x) = (3.50 - 2) x - 4
P (x) = 1.50x - 4
Answer:
An equation to model the amount of profit, P, the band makes from x rolls of wrapping paper in one week is:
P (x) = 1.50x - 4