问题 解答题
解方程.
(1)
5
12
x=
7
8
(2)x+
1
6
=
8
5
(3)
30
7
÷x=
2
28
(4)50%x+30%x=8(5)x-20%x=40.
答案

(1)

5
12
x=
7
8

5
12
12
5
=
7
8
×
12
5

x=2.1;

(2)x+

1
6
=
8
5

x+

1
6
-
1
6
=
8
5
-
1
6

x=

43
30

(3)

30
7
÷x=
2
28

30
7
÷x×x=
1
14
×x,

1
14
x=
30
7

1
14
x×14=
30
7
×14,

x=60;

(4)50%x+30%x=8,

(50%+30%)x=8,

0.8x=8,

0.8x÷0.8=8÷0.8,

x=10;

(5)x-20%x=40,

(1-20%)x=40,

0.8x=40,

0.8x÷0.8=40÷0.8,

x=50.

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