There are 5 + 8 + 7 = 20 students in the first three groups. There are 24 - 20 = 4 students in the fourth group.
The answer: 4
Reverse engineering the question: The teacher divided the students into four groups. One group had 5 students, another 8 students, and the third 7 students. If there were 24 total students, how many students were in the fourth group?


Reasoning and answer: Let s be the number of gallons of seed Carson uses and f be the number of gallons of fertilizer. We know that s = 3f and s + f = 60. Substituting the first equation into the second equation produces 3f + f = 60. Combining like terms, we get 4f = 60. Dividing both sides by 4, we get f = 15. Substituting that value into the equation s = 3f, we get s = 3 * 15 = 45.
The answer: 45
What was the question?
Question: Carson is covering the high school football field with grass seed. Each square meter needs three times as much seed as fertilizer. If Carson uses 60 gallons of seed and fertilizer combined, how many gallons of seed does he use?


He collects 25 leaves because 12 + 13 = 25. 60% of them are yellow because 100 - 20 - 20 = 60. He collects 15 yellow leaves because 25 x .6 = 15.
The answer: 15
Reverse engineering the question: Bronson decides to collect Oak Leaves from around his Neighborhood. He collects 12 on Thursday and 13 on Friday. 20% are Brown and 20% are Green. The rest are yellow. How many yellow leaves does he collect?


Reasoning and answer: If James bought 400 fish, the number of fish that were bad is 20 / 100 * 400 = 80. The remaining fish that he used to make the sushi rolls is 400 - 80 = 320. If 40 fish are required to make one sushi roll, 320 fish will make 320 / 40 = 8 sushi rolls.
The answer: 8
What was the question?
Question: James needs 40 fish to make one sushi roll. He goes to the market and buys 400 fish, but later finds out that 20% of the fish have gone bad and cannot be used. How many sushi rolls did James make with the remaining fish?


Dimitri saw 2 x 6 = 12 wheels on the bicycles. He saw 15 x 3 = 45 wheels on the tricycles. He saw a total of 12 + 45 = 57 wheels.
The answer: 57
Reverse engineering the question: At the park, Dimitri saw families riding bicycles and tricycles. Bicycles have two wheels and tricycles have three wheels. 6 adults were riding bicycles and 15 children were riding tricycles.  How many wheels did Dimitri see at the park?


He bought 3 * 12 = 36 eggs. So they cost 36 * .5 = $18.
The answer: 18
Reverse engineering the question:
Tim buys 3 dozen eggs. Eggs cost $.50 each. How much did he pay for eggs?