(1)2-1/5-1/3-4/5
=2-4/3
=2/3
(2)0.8加5/8加0.2=1加5/8=1又5/8=13/8
(3)15-5/16-11/16
=15-1
=14
(4)25×5.7-5.7×24
=(25-24)×5.7
=5.7