How are the expressions 8-15 and 8 - (-15) ? how are they different?

8 - 15 means subtract the positive number 15 from 8.

8 - 15 = 8 + (-15) = - 7

8 - (-15) means subtract the negative number - 15 from 8.

Subtracting a negative number is the same as adding a positive number.

8 - (-15) = 8 + 15 = 23

8 - 15 = - 7, and 8 - (-15) = 23. The expressions mean different operations and have different answers.