Me with this i have absolutely no idea what the answer is!

A. Her expenses are $25 per week.  

Step-by-step explanation:

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.

both equations and proportions are better.