We look first for the total number of books that were sold: 60 + 10 + 20 + 44 + 66 = 200 books. So the total number of books that were not sold is: 800 – 200 = 600 books.
The answer: 600
Reverse engineering the question: Ali had a stock of 800 books in his Room. He sold 60 on Monday, 10 on Tuesday, 20 on Wednesday, 44 on Thursday and 66 on Friday. How many books were not sold?

Luke started putting together, 1000 x 0.1 = 100 pieces. The next day, there were 1000 - 100 = 900 pieces left. Then he put together 900 * 0.2 = 180 pieces on the second day. So there were 900 - 180 = 720 pieces left. On the third day, he put together 720 * 0.3 = 216 pieces. Therefore, Luke still has 720 - 216 = 504 pieces left to complete the puzzle.
The answer: 504
Reverse engineering the question: Luke started working on a 1000-piece jigsaw puzzle. The first day he worked on it, he put together 10% of the pieces. On the second day, he put together another 20% of the remaining pieces from the first day. On the third day, he put together 30% of the remaining pieces from the previous day. How many pieces does he have left to complete after the third day?

Let z be the number of zoology books and b be the number of botany books. We know that z + b = 80 and b = 4z. Substituting the second equation into the first equation, we get z + 4z = 80. Combining like terms, we get 5z = 80. Dividing both sides by 5, we get z = 16.
The answer: 16
Reverse engineering the question: Milton has some books about zoology and 4 times as many books about botany. If he has 80 books total, how many zoology books does he have?

The company has chopped down a total of 200 + 300 = 500 trees throughout the year. They plant 3 trees for every tree they chop so they need to plant 500 trees * 3 = 1500 trees.
The answer: 1500
Reverse engineering the question:
A paper company decides to operate their business more sustainably. They decide that for every tree they chop down, they want to plant three more. If the company chops down 200 trees in the first half of the year and 300 more trees in the second half of the year, how many more trees does the company need to plant?