Explain why it is possible to say that we really don't need to have a rule for subtraction of signed numbers

Question

Explain why it is possible to say that we really don't need to have a rule for subtraction of signed numbers. (This involves using the additive inverse.)

Answer 1

If subtraction is defined by using the additive inverse [ 6 - 2 means 6 + -2], then the question answers itself. So how is subtraction defined in your class? a - b means a + (-b)? So you get the classic "add the opposite" rule.

Answer 2

because we could use our brains and realize its not that hard to do it logically.