0.325乘0.8加0.55除以5/4减3/5除以8/7
=0.325×0.8+0.55×4/5-3/5×7/8
=（0.325+0.55）×0.8-3/5×7/8
=7/8×0.8-3/5×7/8
=7/8×（0.8-3/5）
=7/8×1/5
=7/40