（1）
0.75*0.25*3.2
=3/4*1/4*16/5
=3/16*16/5
=3/5
（2）
4.8/0.5/0.2
=4.8×2/0.2
=4.8×(2/0.2)
=4.8*10
=48
(3)
(5.4+3.6)*6.5+6.5
=9*6.5+6.5
=6.5*(9+1)
=6.5*10
=65