In the past four months, not including today, Erica has 80 kg * $20 / kg = $1600 worth of fish. Today, Erica trawled 80 * 2 = 160 kg of fish. Thus today's earnings are 160 kg * $20 / kg = $3200. Her total earnings are $3200 + $1600 = $4800.
The answer: 4800
Reverse engineering the question: Erica lives near a lake where most locals sell fish as their main source of income, earning $20 per kg of fish. She goes out fishing today and catches twice as many fish as she caught in total in the past four months. If Erica trawled 80 kg of fish in the past four months, not including today, how much money will she have earned in the past four months including today (assuming she sells all her fish)?

He releases 1 video that is 2 * 6 = 12 minutes long. So each day he releases 2 + 2 + 12 = 16 minutes of videos. That means he releases 16 * 7 = 112 minutes of videos.
The answer: 112
Reverse engineering the question: John releases 3 videos on his channel a day. Two of them are short 2 minute videos and 1 of them is 6 times as long. Assuming a 7-day week, how many minutes of video does he release per week?

The ten people donated 10 * 5 = 50 books. The total number of books in her store after the new donations is 300 + 50 = 350 books. When some of the books are borrowed, her total collection becomes 350 - 140 = 210 books.
The answer: 210
Reverse engineering the question: Tracy has a charity book collection store from which she receives book donations from members of her town. Any person who wants to borrow a book is free to do so as long as they return the book after they've finished reading. She has already received 300 book donations. If ten people come and donate five books each in a week, and a total of 140 books are borrowed by other people to read, calculate the total number of books she has remaining in the store?

Each trip, they add Caleb’s 7 gallons + Cynthia’s 8 gallons = 15 gallons. Since they are adding 15 gallons every trip, to fill the 105 - gallon pool, it would take 105 / 15 = 7 trips.
The answer: 7
Reverse engineering the question:
Caleb and Cynthia are filling up their inflatable pool with water using buckets. They fill their buckets at the spigot and carry them to the pool. Caleb can add 7 gallons from his bucket and Cynthia can add 8 gallons from her bucket each trip. It will take 105 gallons to fill the pool. How many trips will it take for Caleb and Cynthia to fill the pool with their buckets?