When the price of the book is decreased by 15%, the total price decrease is 15 / 100 * $400 = $60. The new price of the book becomes $400 - $60 = $340. The price of the book is then increased by 40 / 100 * 340 = $136. The final price of the book is $340 + $136 = $476.
The answer: 476
Reverse engineering the question: The price of a book was $400. If the book's price is decreased by 15% and then increased by 40%, what is the final price of the book?

Last year, there were a total of 100 + 50 = 150 books in the library. The library purchased 50 x 3 = 150 books this year. Therefore, the library now has a total of 150 + 150 = 300 books.
The answer: 300
Reverse engineering the question: Last year, the school library purchased 50 new books. This year, it purchased 3 times as many books. If the library had 100 books before it purchased new books last year, how many books are in the library now?

He lost 700 * .3 = 210 pounds on squat. So his squat is now 700 - 210 = 490 pounds. His deadlift is 800 - 200 = 600 pounds. So his total is now 490 + 600 + 400 = 1490 pounds.
The answer: 1490
Reverse engineering the question: John used to go to the gym multiple times a weak but because of lockdowns he hasn't been able to go. He used to lift 700 for squat, 400 for bench, and 800 for deadlift. For squat he lost 30% of his lift. He didn't lose any weight on bench because he was able to train that at home and he lost 200 pounds on deadlift. What is his new total?

The combined cost of everything was 2500 + 3500 + 2000 = $8000. So he gets an 8000 * .1 = $800 discount. That means he pays 8000 - 800 = $7200.
The answer: 7200
Reverse engineering the question:
James decides to buy a living room set. The coach cost $2500 and the sectional cost $3500 and everything else has a combined cost of $2000. He gets a 10% discount on everything. How much did he pay?