问题 解答题
求未知数X
1
2
x-25%x=10
1÷(
4
5
x-
1
5
)=3
8
21
=
0.4
x
答案

(1)

1
2
x-25%x=10,

0.25x=10,

0.25x÷0.25=10÷0.25,

x=40;

(2)1÷(

4
5
x-
1
5
)=3,

1÷(

4
5
x-
1
5
)×(
4
5
x-
1
5
)=3×(
4
5
x-
1
5
),

1=

12
5
x-
3
5

1+

3
5
=
12
5
x-
3
5
+
3
5

8
5
=
12
5
x,

8
5
÷
12
5
=
12
5
x÷
12
5

x=

2
3

(3)

8
21
=
0.4
x

8x=21×0.4,

8x=8.4,

8x÷8=8.4÷8,

x=1.05.

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