Who had the least amount of money, and how much was it?

When Anne, Betty and Cynthia compared the amount of money each had they discovered that Anne and Betty together had $12, Betty and Cynthia together had $18, and Anne and Cynthia together had $10. Who had the least amount of money, and how much was it?

Let A, B and C represent the amount of money and Anne, Betty and Cynthia has.

A+B = 12
B+C = 18
A+C = 10

As A+B and A+C is less than B + C => Anne has the least amount of money.

Adding all three equations, A+B+B+C+A+C = 12+18+10 = 40
2A+2B+2C = 40
A+B+C = 20
Substituting B+C = 18
A+18 = 20
A = 2

Anne has $2.

Anne has the least amount of money and she has $2.