6*《9/8-8/7》*《-12》
=-72*《9/8-8/7》
=-72*9/8+72*8/7
=-64+63
=-1
《3/1-3+6/1-12/7》*《-6》2次方
=《3/1-3+6/1-12/7》*36
=3/1*36-3*36+6/1*36-12/7*36
=12-108+6-21
=-111