a) 14/15-2/15+17/20-7/20=
56/60-8/60+51/60-21/60=48/60+51/60-21/60=99/60-21/60=78/60=26/20=13/10
b) 5/7-3/7+3/14+5/14=10/14-6/14+3/14+5/14=4/14+3/14+5/14=7/14+5/14=12/14=6/7
c) 8/15X(15/16:3/8X3/4)=8/15X(15/16:6/16X12/16)=8/15X(15/16X16/6X12/16)=
8/15X(240/96X12/16)=8/15X2880/1536=23040/23040=1
d) 9/10:[(3 5/8-1 3/8):2 1/2]=9/10:[(29/8-11/8):5/2]=9/10:[18/8:5/2]=9/10:[18/8X2/5]=9/10:36/40=9/10X40/36=360/360=1
