问题 解答题
解方程.
x+
7
9
x=
4
3

2
3
1
4
=12
5X-3×
5
21
=
5
7
答案

(1)x+

7
9
x=
4
3

(1+

7
9
)x=
4
3

16
9
x=
4
3

16
9
9
16
=
4
3
×
9
16

x=

3
4

(2)

2
3
1
4
=12,

2
3
1
4
×4=12×4,

2
3
X=48,

2
3
3
2
=48×
3
2

X=72;

(3)5X-3×

5
21
=
5
7

5X-

5
7
=
5
7

5X-

5
7
+
5
7
=
5
7
+
5
7

5X=

10
7

5X÷5=

10
7
÷5,

X=

2
7

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