Phil started with 50, and doubled this amount the next year for 50 * 2 = 100 coins. Phil then collected 3 per month the following year, and since there are 12 months in a year that was 3 * 12 = 36 coins added. Phil then collected 1 every third month, and since there are 12 months that means he collected one every 12 / 3 = 4 months, for 4 coins added. Before he lost a quarter of his coins, Phil had 100 + 36 + 4 coins, or 140 coins in total. Losing a quarter of 140 coins means Phill lost 140 / 4 = 35 coins. That means Phil had 140 - 35 = 105 coins remaining.
The answer: 105
Reverse engineering the question: Phil has a coin collection he likes to add to. He started with 50 state quarters his parents gave him. Over the next year he doubled this. The following year he collected 3 each month. The year after that he collected 1 every third month. The year after that he lost a quarter of them when he misplaced his collection. How many did he have left after losing some?

The contractor works for 3 * 5 = 15 hours. That means he charged 150 * 15 = $2250. The inspector charged 2250 * .8 = $1800 less. So the inspector charged 2250 - 1800 = $450. So the total amount charged was 250 + 450 + 2250 = $2950.
The answer: 2950
Reverse engineering the question: John decides to install a ramp in his house. He needs to get permits which cost $250. After that, he hires a contractor which costs $150 an hour and the guy works for 3 days at 5 hours per day. He also pays an inspector 80% less to make sure it is OK. How much was the total cost?

The pistachios cost 10 / 5 = $2 per ounce. He eats 30 / 5 = 6 ounces of pistachios a day. So he spends 6 * 2 = $12 per day on pistachios. So he spends 12 * 7 = $84 per week.
The answer: 84
Reverse engineering the question: James buys pistachios for $10 per can. Each can is 5 ounces. He eats 30 ounces of pistachios every 5 days. How much does he spend on pistachios per week?

Rene finished 30 x 4 = 120 pages in 240 minutes. Lulu finished 27 x 4 = 108 pages in 240 minutes. Cherry finished 25 x 4 = 100 pages in 240 minutes. Therefore they have finished a total of 120 + 108 + 100 = 328 pages in 240 minutes.
The answer: 328
Reverse engineering the question:
Rene can finish reading 30 pages in 60 minutes. Lulu can read 27 pages in 60 minutes and Cherry can read 25 pages in 60 minutes. If they have been reading for 240 minutes now, how many pages have they finished reading in total?