480/15-2.4/1.5
=480/15-24/15
=（480-24）/15）
=456/15
=456/3/5
=152/5
=30.4
3/8/[(1/3+1/4)]/5/6
=3/8/[7/12]/5/6
=3/8*12/7*6/5
=9/14*6/5
=27/35