Let X be the number of chickens Mr. Rainwater has. He has 4 goats / cow * 9 cows = 36 goats on his farm. So he has 36 goats / 2 goats / chicken = 18 chickens.
The answer: 18
Reverse engineering the question: Mr. Rainwater has some goats, 9 cows and some chickens. He has 4 times as many goats as cows and 2 times as many goats as chickens. How many chickens does he have?

In 11 months, Yoque will pay a total of $15 x 11 = $165. The amount $165 is 100% + 10% = 110% of the money she borrowed. So, 1% is equal to $165 / 110 = $1.50. Hence, Yoque borrowed $1.50 x 100 = $150.
The answer: 150
Reverse engineering the question: Yoque borrowed money from her sister. She promised to pay it back in 11 months including an additional 10% of the money she borrowed. If she pays $15 per month, how much money did she borrow?

It costs Jen 80 * 50 = 4000 cents to buy 50 candy bars. Since a dollar is 100 cents, she earns 48 * 100 = 4800 cents by selling 48 of them. Thus her total profit is 4800 - 4000 = 800 cents.
The answer: 800
Reverse engineering the question: Jen buys and sells candy bars. She buys candy bars for 80 cents each and sells them for a dollar each. If she buys 50 candy bars and sells 48 of them, how much profit does she make in cents?

Every second month Nina does twice the regular distance, which means 400 * 2 = 800 kilometers. Two years is 24 months, so half of this time is 24 * 0.5 = 12 months. So in 12 months Nina does 400 * 12 = 4800 kilometers. And in the other 12 months, she does 800 * 12 = 9600 kilometers. So in two years, Nina would be able to make 4800 + 9600 = 14400 kilometers.
The answer: 14400
Reverse engineering the question:
Nina loves to travel. She tries to travel at least 400 kilometers in one month outside of her home country. Every second month she does twice that distance. If she were able to keep up with her resolution, how many kilometers would she travel during 2 years?