Q: Roxanne bought 2 cups of lemonade for $2 each and 2 sandwiches for $2.50 each. How much change must she get from a $20 bill?
A: Two cups of lemonade amount to $2 x 2 = $4. Two sandwiches amount to $2.50 x 2 = $5. So, the total amount that Roxanne had to pay was $4 + $5 = $9. Thus, her change must be $20 - $9 = $11. The answer is 11.

Q: The moon has a surface area that is 1/5 that of Earth. The surface area of the Earth is 200 square acres. The land on the moon is worth 6 times that of the land on the Earth. If the total value of all the land on the earth is 80 billion dollars, what is the total value in billions of all the land on the moon?
A: If the moon land had the same value as earth land it would be worth 16 billion because 80 / 5 = 16. The moon's total land value is 96 billion because 16 x 6 = 96. The answer is 96.

Q: In seven years, Talia will be 20 years old. Talia's mom is currently three times as old as Talia is today. In three years, Talia's father will be the same age as Talia's mom is today. Currently, how many years old is Talia's father?
A:
In seven years, Talia will be 20 years old, and therefore Talia is currently 20 - 7 = 13 years old. Talia's mom is currently three times as old as Talia is today, or 3 * 13 = 39 years old. If in three years, Talia's father will be the same age as Talia's mom is today, then Talia's father is currently 39 - 3 = 36 years old. The answer is 36.