### Instruction: Together, Amy and Betty have 20 apples. Amy has three times the number of apples that Betty has. How many more apples than Betty does Amy have?### Response: I need to find the difference between the number of apples that Amy and Betty have.
I can use algebra to represent the situation with variables and equations.
Let x be the number of apples that Betty has, and let y be the number of apples that Amy has.
Then I have two equations: x + y = 20 and y = 3x.
I can substitute y = 3x into the first equation and get x + 3x = 20.
Simplifying, I get 4x = 20, so x = 5.
This means that Betty has 5 apples and Amy has 3 times as many, so y = 3x = 15.
To find the difference, I subtract the smaller number from the larger number: y - x = 15 - 5 = 10.
So Amy has 10 more apples than Betty.