(1)1 ÷
3
4 ×3-
5
12 ÷2,
=
4
3 ×3-
5
12 ÷2,
=4-
5
12 ×
1
2 ,
=4-
5
24 ,
=3
19
24 ;
答:差是3
19
24 .
(2)(5.5+0.8)÷(1-
2
5 ),
=6.3÷0.6,
=10.5;
答:商是10.5.
(3)设这个数是x,由题意得:
3
5 x+1.7=18.5×20%,
3
5 x+1.7=3.7,
3
5 x+1.7-1.7=3.7-1.7,
3
5 x=2,
3
5 x÷
3
5 =2÷
3
5 ,
x=
10
3 .
答:这个数是
10
3 .