问题 解答题
解方程:
①X+
1
3
X=620

②X-
2
7
X=450
1
4
+2X=2.5
④X(1+
1
5
)=78.
答案

(1)X+

1
3
X=620,

4
3
X=620,

4
3
3
4
=620×
3
4

X=465;

(2)X-

2
7
X=450,

5
7
X=450,

5
7
7
5
=450×
7
5

X=630;

(3)

1
4
+2X=2.5,

1
4
+2X-
1
4
=2.5-
1
4

2X÷2=2.25÷2,

X=1.125;

(4)X(1+

1
5
)=78,

6
5
X=78,

6
5
5
6
=78×
5
6

X=65.

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