The oldest brother is 15 because 3 x 5 = 15. Michael is 8 because if 1 + (Michael's age - 1) x 2 = 15 then Michael's age = 8. Their combined age is 28 because 5 + 15 + 8 = 28.
The answer: 28
Reverse engineering the question: Michael has two brothers. His oldest brother is 1 year older than twice Michael's age when Michael was a year younger. His younger brother is 5 years old, which is a third of the age of the older brother. What is their combined age?

Let p be the cost of a full - priced pen. We know that the first 10 pens are sold at the regular price, so they cost 10 * p. We also know the any pens purchased after the first 10 are half - price, so they cost (20 pens - 10 pens) * p / 2 on those. If we add the cost of the first 10 pens and the pens sold at half - price it equals the total purchase of price of $30 = 10 * p + (20 - 10) * p / 2. Thus, $30 = 10 * p + 10 * p / 2. And, $30 = 10 * p + 5 * p. So, $30 = 15 * p. Finally, p = $2.
The answer: 2
Reverse engineering the question: A shop is offering a discount on pens. If you buy 10 pens at the regular price, you can get the next 10 for half off. A customer came in and bought 20 pens for $30. What's the regular price of one pen in dollars?

During the weekdays it was visited by 100 * 5 = 500 people. On Sunday and Saturday, it was visited by 200 + 300 = 500 people. In total 500 + 500 = 1000 people visited the park in a week. So it earned 1000 * 3 = 3000 dollars in a week.
The answer: 3000
Reverse engineering the question: An amusement park sells tickets for $3. This week it welcomed 100 people per day but on Saturday it was visited by 200 people and on Sunday by 300. How much money did it make overall in a week?

First find the number of quarts the hot tub holds by multiplying the number of gallons it holds by 4: 40 gallons * 4 quarts / gallon = 160 quarts. Then multiply the number of quarts of champagne Jackson buy by the normal price per bottle to find the cost before the discount: 160 quarts * $50 / quart = $8000. Then multiply that number by 20% to find the amount of the discount: $8000 * .2 = $1600. Finally, subtract the discount from the total cost to find the final amount Jackson pays: $8000 - $1600 = $6400.
The answer: 6400
Reverse engineering the question:
Jackson wants to impress his girlfriend by filling her hot tub with champagne. The hot tub holds 40 gallons of liquid. Each bottle of champagne holds 1 quart. (There are 4 quarts per gallon). If each bottle of champagne costs $50, but Jackson gets a 20% volume discount, how much does he spend on champagne?