Tina pet sits to earn extra money. She charges a flat service fee of $20, plus $15 per day. If one of her customers spent less than $110, which of the following inequalities could be used to solve for x, the number of days the customer paid for pet sitting?
A. $15x - $20 < $110
B. $15x < $130
C. $15x < $110
D. $15x + $20 < $110