[Question]: The total number of books on four shelves, with 400 books each, is the same as the distance in miles that Karen bikes back to her home from the library. Calculate the total distance that Karen covers if she bikes from her home to the library and back.
[Answer]: If each shelf has 400 books, then the four shelves have 4 * 400 = 1600 books. Since the total number of books on the shelves is the same as the distance that Karen bikes back home, biking to and from the library takes 1600 + 1600 = 3200 miles.
So the answer is 3200.

[Question]: After buying shirts worth $27 from a store, Dennis received 2 $10 bills and $3 in loose coins for his change. How much money did Dennis have initially?
[Answer]: Dennis received $10 x 2 = $20. So, he received a total of $20 + $3 = $23 change. Therefore, Dennis initially had $27 + $23 = $50.
So the answer is 50.

[Question]: A teacher teaches 5 periods a day and works 24 days a month. He is paid $5 per period. if he has been working for 6 months now how much has he earned in total?
[Answer]:
The amount paid to the teacher per day is 5 periods * $5 / period = $25 per day. The amount paid for 24 days is $25 / day * 24 days = $600. The total amount for 6 months is $600 * 6 = $3600.
So the answer is 3600.