Jessica is selling books during the summer to earn money for college. she earns a commission on each sale but has to pay for her own expenses. after a month of driving from neighborhood to neighborhood and walking door-to-door, she figures out that her weekly earnings are approximately a linear function of the number of doors she knocks on. she writes the equation of the function like this: e(x) = 10x - 35, where x is the number of doors she knocks on during the week and e(x) is her earnings for the week in dollars.