Using a linear function f(x) = mx + b, m= slope and b = y-intercept or initial value. With the values of the given function: E(x) = 7x - 25, we can determine that the overall earnings (E(x)) is based on a profit of $7 per door ('x') and that if Jessica is subtracting $25 from her earnings, that this must be the cost per week for her expenses. So, she would need to knock on a minimum of 4 doors each week in order to make a profit.
