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Bài làm
a)100-7.(X.5)=58
7.(X.5)=100-58
7.(X.5)=42
X.5=42:7
X.5=6
X =6:5
X=1,2.
#)Giải :
a) \(100-7\times\left(x\times5\right)=58\)
\(\Leftrightarrow7\times\left(x\times5\right)=42\)
\(\Leftrightarrow x\times5=6\)
\(\Leftrightarrow x=1,2\)
b) \(x\times\frac{2}{7}=\frac{242}{363}\times\frac{1616}{2121}\)
\(\Leftrightarrow x\times\frac{2}{7}=\frac{2}{3}\times\frac{16}{21}\)
\(\Leftrightarrow x\times\frac{2}{7}=\frac{32}{63}\)
\(\Leftrightarrow x=\frac{16}{9}\)
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a. -12 (x-5) +7(3-x) = -12x+60+21-7x=-19x+81=15
=> -19x=15-81=-66
=> x=66/19
b. 30(x+2) - 5 (x-5) - 24x = 30x+60-5x+25-24x =(30x-5x-24x)+(60+25)=x+85=100
=> x=100-85=15
![](https://rs.olm.vn/images/avt/0.png?1311)
mk chỉnh lại cái đề bài ý a
30(x+2)-6(x-5)-24x=100
![](https://rs.olm.vn/images/avt/0.png?1311)
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a.-12 ( x-5 ) +7 (3-x) = 5
-12x +60 + 21 - 7x =5
60+21-5 = 12x + 7x
76 = 19x
x = 4
b.30(x +2) - 6(x-5) -24x = 100
30x+60 - 6x -30-24x = 100
60-30-100 = 30x -6x - 24x
-70 = 0x
x = -70
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a :
[( 10 - x ) . 2 + 5] : 3 - 2 = 3
( 10 - x ) x 2 + 5 = ( 3+2) x 3
( 10 - x ) x 2 + 5 = 15
10 -x = ( 15 -5 ) : 2
10 - x = 5
x = 5
a) \(\left[\left(10-x\right)2+5\right]:3-2=3\)
\(\left(20-2x+5\right):3-2=3\)
\(\left(20-2x+5\right):3=5\)
\(20-2x+5=15\)
\(20-2x=10\)
\(2x=10\)
\(x=5\)
b) \(6x-302=2^3\cdot5\)
\(6x=8\cdot5+302\)
\(6x=342\)
\(x=57\)
c) \(12\left(x-1\right):3=4^3-2^3\)
\(12\left(x-1\right):3=56\)
\(12\left(x-1\right)=168\)
\(x-1=12\)
\(x=13\)
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