3/4*1/6+2/3*1/4
=1/4x3/6+1/4x2/3
=1/4x(3/6+2/3)
=1/4x7/6
=7/24
15/16*15
=(1-1/16)x15
=1x15-1/16x15
=15-15/16
=14又1/16
53/54* 55
=53/54x(54+1)
=53/54x54+53/54x1
=53+53/54
=53又53/54