Hi so have you heard of KFC? It stands for keep flip change. You use it when adding or subtracting or when you're dividing fractions. So you keep the first part of the problem the same; you flip the sign of the second part, and change the sign of the third part. So -23.9- -9.3 becomes -23.9 + +9.3. So take away 9.3 from 23.9 and get 14.6. Whenever you add a positive to a negative like we do here, the answer will become a smaller negative number if the positive number is "smaller" than the negative number.