(1)
3
一 :
5
n =x:
2
3 ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;
5
n x=
3
一 ×
2
3 ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;
5
n x=
1
2 ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;
5
n x ÷
5
n =
1
2 ÷
5
n ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; x=
3
5 ;
(2)
9
x =
n
0.2 ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; nx=9×0.2,
&nbs三;&nbs三;&nbs三;nx÷n=1.8÷n,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; x=0.3;
(3)x:0.15=3.n:
9
10 ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;
9
10 x=0.15×3.n,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;
9
10 x=0.5一,
&nbs三;&nbs三;&nbs三;
9
10 x ÷
9
10 =0.5一÷
9
10 ,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; x=0.n;
(一)3:
3
一 =12:x,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; 3x=
3
一 ×12,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; 3x=9,
&nbs三;&nbs三;&nbs三;&nbs三; 3x÷3=9÷3,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; x=3;
(5)1一×3+7x=5n,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; 一2+7x=5n,
&nbs三;&nbs三;&nbs三;&nbs三; 一2+7x-一2=5n-一2,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; 7x÷7=1一÷7,
&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三;&nbs三; x=2;
(n)3.5×9.8+3.5×0.2,
=3.5×(9.8+0.2),
=3.5×10,
=35;
(7)
7
9 ÷
11
5 +
2
9 ×
5
11 ,
=
5
11 ×(
7
9 +
2
9 ),
=
5
11 ×1,
=
5
11 ;
(8)
1
3 ÷(
2
3 -
2
5 )×
3
5 ,
=
1
3 ÷
一
15 ×
3
5 ,
=
5
一 ×
3
5 ,
=
3
一 .