Shelby had $20 to take to the book fair. She bought one book for $8 and another for $4. She decided to buy as many $4 posters as she could with the money she had left. How many posters can she buy? Give the rationale and then the answer.
Let's think step by step. She spent $8 + $4 = $12 on books. She started with $20, so she has $20 - $12 = $8 left to spend on posters. Each poster costs $4, so she can buy $8 / $4 = 2 posters.. The answer is: 2.

A king gets a crown made that costs $20,000. He tips the person 10%. How much did the king pay after the tip? Give the rationale and then the answer.
Let's think step by step. The tip was 20000 * .1 = $2000. So the total cost was 2000 + 20000 = $22000.. The answer is: 22000.

Melody has three dogs. Each dog eats 1/2 of a pound of dog food twice a day. If Melody bought 30 pounds of dog food, how many pounds of dog food are left after a week? Give the rationale and then the answer.
Let's think step by step. Each dog eats 1 / 2 x 2 = 1 pound of dog food each day. So the three dogs eat a total of 1 x 3 = 3 pounds each day. That is 3 x 7 = 21 pounds in a week. Therefore, 30 - 21 = 9 pounds of food are left after a week.. The answer is: 9.