5/17*(-3/7)+5/17*(-4/7)-12/17
=5/17*(-3/7-4/7)-12/17
=5/17*(-1)-12/17
=-5/17-12/17
=-1
(-0.75)*(-3又1/8)-0.75*(-4又7/8)
=0.75*(3又1/8)+0.75*(4又7/8)
=0.75*(3又1/8+4又7/8)
=0.75*8
=6
5/17*(-3/7)+5/17*(-4/7)-12/17
=5/17*(-3/7-4/7)-12/17
=5/17*(-1)-12/17
=-5/17-12/17
=-1
(-0.75)*(-3又1/8)-0.75*(-4又7/8)
=0.75*(3又1/8)+0.75*(4又7/8)
=0.75*(3又1/8+4又7/8)
=0.75*8
=6