（2-0.125）*8
=2*8-0.125*8
=16-1
=15
3.6/[0.25*（17.3 +30.7）]
=3.6/[0.25*48]
=3.6/[0.25*(40+8)]
=3.6/[0.25*40+0.25*8]
=3.6/[10+2]
=3.6/12
=0.3