Question

A commuter has $245 in his computer savings account. This account changes by -$15 each week he buys a ticket. In one time period, the account changed by -$240. For how many weeks did the commuter buy tickets? How much must he add to his account if he wants to have 20 weeks worth of tickets in his account?

Answer 1

He paid $15 per ticket, once a week, so:
240 / 15 = 16
The commuter bought tickets for 16 weeks.

If he wants 20 weeks' worth of tickets, he must pay $15 for each ticket,
so 20 x 15 = $300. He needs $300 to buy 20 weeks' worth of tickets.