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a)X:10+2X9,9=30,25
X:10+2 =30,25:9,9=3,05
X:10 =3,05+2=5,05
X =5,05x10=50,5
x:10+x*9,9=30,25
x*0,1+x*9.9=30,25
x*(0,1+9,9)=30,25
x*10=30,25
x=30.25:10=3,025
\(x:100+x.0,99=5,25\)
\(\Leftrightarrow x.\frac{1}{100}+x.\frac{99}{100}=\frac{21}{4}\)
\(\Leftrightarrow x.\left(\frac{1}{100}+\frac{99}{100}\right)=\frac{21}{4}\)
\(\Leftrightarrow x.1=\frac{21}{4}\)
\(\Leftrightarrow x=\frac{21}{4}\)
a, x . 9,9 + x : 10 = 12,5
\(x.\frac{99}{10}+x.\frac{1}{10}=\frac{25}{2}\)
\(x\left(\frac{99}{10}+\frac{1}{10}\right)=\frac{25}{2}\)
\(x.10=\frac{25}{2}\)
\(x=\frac{25}{2}:10=\frac{25}{2}.\frac{1}{10}=\frac{5}{4}\)
b, \(x:\frac{1}{4}-x=\frac{78}{5}\)
\(x.4-x=\frac{78}{5}\)
\(x\left(4-1\right)=\frac{78}{5}\)
\(x.3=\frac{78}{5}\)
\(x=\frac{78}{5}:3=\frac{78}{5}.\frac{1}{3}=\frac{26}{5}\)
c, \(x:\frac{1}{10}-x:4-x.\frac{3}{4}=\frac{9}{4}\)
\(=x.10-x.\frac{1}{4}-x.\frac{3}{4}=\frac{9}{4}\)
\(x\left(10-\frac{1}{4}-\frac{3}{4}\right)=\frac{9}{4}\)
\(x.9=\frac{9}{4}\)
\(x=\frac{9}{4}:9=\frac{9}{4}.\frac{1}{9}=\frac{1}{4}\)
****
\(x\cdot9,9+x:10=12,5\)
\(x\cdot9,9+x\cdot\frac{1}{10}=12,5\)
\(x\cdot\left(9,9+\frac{1}{10}\right)=12,5\)
\(x\cdot\left(\frac{99}{10}+\frac{1}{10}\right)=12,5\)
\(x\cdot\frac{100}{10}=12,5\)
\(x\cdot10=12,5\)
\(x=12,5:10\)
\(x=1,25\)
Vậy x = 1,25
a) \(x\times9+x\div10=45\)
\(x\times\left(9,9+10+0,1\right)=45\)
\(x\times10=45\)
\(x=45\div10\)
Suy ra \(x=4,5\)
b) \(x\div100+x\times9,99=42,9\)
\(x\div100=42,9\times\left(9,99+0,01\right)\)
\(x\div100=429\)
\(x=429\div100\)
Suy ra \(x=4,29\)
a,Ta có: x*9,9+x:10=45 b,x:100+x*9,99=42,9
x*9,9+x*0,1=45 x*0,01+x*9,99=42,9
x*(9,9+0,1)=45 x*(0,01+9,99)=42,9
x*10=45 x*10=42,9
x=45:10=4,5 x=42,9:10=4,29
Vậy x=4,5 Vậy x=4,29
Mọi người tk cho mình nha. Mình cảm ơn nhiều ^-^