问题 解答题
解下列方程.
7
8
x=
21
40

1
3
4
5
=8
x+20×
1
4
=19
x+
7
8
x=42.
答案

(1)

7
8
x=
21
40

7
8
7
8
=
21
40
÷
7
8

x=

3
5

(2)

1
3
4
5
=8

1
3
4
5
×
4
5
=8×
4
5

1
3
x=
32
5

1
3
1
3
=
32
5
÷
1
3

x=

96
5

(3)x+20×

1
4
=19

x+5=19

x+5-5=19-5

x=14

(4)x+

7
8
X=42

(1+

7
8
)X=42

15
8
X=42

15
8
15
8
=42÷
15
8

X=

112
5

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