问题 解答题
求未知数X.
80%X-10=30
2.5:
1
4
=
40
χ
3X-1.2X=36
4
5
X-30%X=2
答案

(1)80%X-10=30,

80%X-10+10=30+10,

80%X=40,

80%X÷80%=40÷80%,

X=50;

(2)2.5:

1
4
=
40
χ

2.5X=

1
4
×40,

2.5X=10,

2.5X÷2.5=10÷2.5,

X=4;

(3)3X-1.2X=36,

1.8X=36,

1.8X÷1.8=36÷1.8,

X=20;

(4)

4
5
X-30%X=2,

0.5X=2,

0.5X÷0.5=2÷0.5,

X=4.

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