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x + 20% * x = 7.2
x +1/5 * x = 7.2
x * ( 1 + 1/5 ) = 7.2
x * 1.2 = 7.2
x = 7.2 : 1.2
x = 6
40% * x + x * 20% = 72
2/5 * x + x * 1/5 = 72
( 2/5 + 1/5 ) * x = 72
0.6 * x = 72
x = 72 : 0.6
x = 120
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\(\left(\frac{3}{20}+\frac{1}{20}-x\right):\frac{32}{9}=\frac{21}{128}\)
\(\Leftrightarrow\frac{4}{20}-x=\frac{21}{128}.\frac{32}{9}\)
\(\Leftrightarrow\frac{1}{5}-x=\frac{7}{12}\)
\(\Leftrightarrow x=\frac{1}{5}-\frac{7}{12}\)
\(\Leftrightarrow x=-\frac{23}{60}\)
Vậy \(x=\frac{-23}{60}\)
Bài làm
\(\left(\frac{3}{20}+\frac{1}{20}-x\right):\frac{32}{9}=\frac{21}{128}\)
\(\left(\frac{3}{20}+\frac{1}{20}-x\right)=\frac{21}{128}.\frac{32}{9}\)
\(\frac{4}{20}-x=\frac{7}{4}.\frac{1}{3}\)
\(\frac{4}{20}-x=\frac{7}{12}\)
\(x=\frac{4}{20}-\frac{7}{12}\)
\(x=\frac{12}{60}-\frac{35}{60}\)
\(x=-\frac{23}{60}\)
Vậy \(x=-\frac{23}{60}\)
\(x=-\frac{37}{15}\)
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Ta có : A=20/11×13 + 20/13×15 +20/15×17+...+20/53×55
A = 10 ×( 2/11×13+2/13×15+...12/53×55)
A = 10 ×(1/11-1/13+1/13-1/15+1/15-1/17+...+1/53-1/55)
A = 10 × (1/11-1/55)
A =10 × 4/55
A = 8/11
![](https://rs.olm.vn/images/avt/0.png?1311)
8,75 * x + 1,25 * x = 20
x * (8,75 + 1,25 ) = 20
x * 10 = 20
x = 20 : 10
x = 2
cau hoi tuong tu
\(8,75.x1,25x=20\)
\(\Rightarrow10x=20\)
\(\Rightarrow x=20:10=2\)
vậy x = 2
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\(15-3\cdot x=20\%\)
\(15-3\cdot x=\frac{1}{5}\)
\(3\cdot x=15-\frac{1}{5}\)
\(3\cdot x=\frac{74}{5}\)
\(x=\frac{74}{5}:3\)
\(x=\frac{74}{15}\)
15 - 3* x = 20%
15 - 3 * x = 1/5
3 * x = 15 - 1/5
3 * x = 74/5
x = 74/5 : 3
x = 74/15
x(8,75+1,285)=20
x.10,035=20
x=20:10,035
x=1,99...
8,75 * x + 1,285 * x = 20
= 8,75 + 1,285
=10,035
= 20 : 10,035
= 1,993024415 nha