there is none. it's like a linguistic phrase. it's not about what the answer is, it's the steps you take to arrive at that answer. bith equal -4, but are done differently. in 3-7, you take 7 out of 3. in -7+3, you put a positive number closer to zero into a negative number further than zero. it's meant to confuse you and make you think it's 10 or -10, but a-b = -b+a. hope this helps!
