Amelias bank account has $300. Each day she withdraws $15. A notification will be sent to her when she has $100 left in her account. Can Amelia withdraw money for 3 weeks without a notification being sent?

No. Amelia wouldn't be able to go three weeks without getting the notification.

3*7=21

300:15=20 means that in twenty days time, Amelia will have withdrawn ALL of her money.

That time period doesn't allow for Amelia to even reach the last day of the third week (21 days).