First find the number of ounces Erin serves per minute: 10 ounces / bowl * 5 bowls / minute = 50 ounces / minute. Then find the number of ounces in the pot: 6 gallons * 128 ounces / gallon = 768 ounces. Then divide the total amount of soup by the amount of soup Erin serves per minute: 768 minutes / 50 ounces / minute = 15.36 minutes, which rounds down to 15 minutes.
The answer: 15
Reverse engineering the question: Erin works in the school cafeteria serving soup. Each bowl of soup has 10 ounces, and Erin can serve 5 bowls per minute. If the pot of soup has 6 gallons of soup, how long will it take Erin to serve all the soup, rounded to the nearest minute? (There are 128 ounces to a gallon.)

Let Mel's weight be m. Brenda’s weight is 3 * m + 10 = 220 pounds. Thus 3m = 220 - 10 = 210 pounds. Therefore Mel's weight is m = 210 / 3 = 70 pounds.
The answer: 70
Reverse engineering the question: Brenda weighs 10 pounds more than 3 times Mel's weight. If Brenda weighs 220 pounds, what is Mel's weight?

George sold 3 cars, so he earned 3 cars * $5 / car = $15 from them. The lego set cost was then $45 - $15 = $30.
The answer: 30
Reverse engineering the question: George was selling some of his old toys on the internet. He managed to sell 3 little cars and a set of Legos. In total, he earned $45. How much did the Legos set cost, if one little car was sold for $5?

Monika spent 24 * 3 = 72 dollars at the movies. Monika spent 20 * 1.25 = 25 dollars at the farmers market. Throughout her day, Monika spent 250 + 72 + 25 = 347 dollars.
The answer: 347
Reverse engineering the question:
Monika went out for the day and spent some money. She went to the mall and spent $250. Then, she went to the movies and watched 3 movies back to back that each cost $24. Then she stopped by the farmer's market on her way home and got 20 bags of beans at $1.25/bag. How much money did Monika spend throughout her day?