Answer: He'd have to work 15 days.
Step-by-step explanation
With the money in his bank account he'd have to get $173 to be able to pay for the rest of the board. If you were to divide 173 by 12 you'd get 14.4166666667. But you can't have a decimal so you'd round up to get a total of 180. Which is how you get the answer of him needing to work for 15 days.