(x+15) :8=7 tìm x
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Bài 1:
a) \(=\dfrac{8}{15}\left(\dfrac{7}{13}+\dfrac{6}{13}\right)=\dfrac{8}{15}.1=\dfrac{8}{15}\)
b) \(=\dfrac{3.3-7-2.4}{12}=-\dfrac{6}{12}=-\dfrac{1}{2}\)
Bài 2:
\(\dfrac{x}{2,7}=-\dfrac{2}{3,6}\Rightarrow x=\dfrac{\left(-2\right).2,7}{3,6}\Rightarrow x=-\dfrac{3}{2}\)
Bài 3:
\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{x+y}{2+5}=-\dfrac{21}{7}=-3\)
\(\Rightarrow\left\{{}\begin{matrix}x=\left(-3\right).2=-6\\y=\left(-3\right).5=-10\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{7}{12}+\frac{x}{15}=\frac{1}{20}\)
=> \(\frac{35}{60}+\frac{4x}{60}=\frac{3}{60}\)
=> 35 + 4x = 3
=> 4x = -32
=> x = -8
b) \(\frac{-7}{x}+\frac{8}{15}=\frac{-1}{20}\)(ĐK \(x\ne0\))
=> \(\frac{-7}{x}=\frac{-1}{20}-\frac{8}{15}\)
=> \(\frac{-7}{x}=\frac{-3}{60}-\frac{32}{60}\)
=> \(\frac{-7}{x}=\frac{-35}{60}\)
=> \(\frac{-7}{x}=\frac{-7}{12}\)
=> x = 12(TM)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
a: Ta có: \(2x+79=x+45\)
nên 2x-x=45-79
hay x=-24
b: Ta có: \(15-\left(x+7\right)=\left(x-8\right)+22\)
\(\Leftrightarrow8-x-x-14=0\)
\(\Leftrightarrow2x=22\)
hay x=11
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a, \(x\) - \(\dfrac{2}{7}\) = \(\dfrac{4}{5}\) \(\times\) \(\dfrac{15}{24}\)
\(x\) - \(\dfrac{2}{7}\) = \(\dfrac{1}{2}\)
\(x\) = \(\dfrac{1}{2}\) + \(\dfrac{2}{7}\)
\(x\) = \(\dfrac{11}{14}\)
b, \(x\): \(\dfrac{2}{7}\) = \(\dfrac{9}{8}\) - \(\dfrac{15}{6}\)
\(x\): \(\dfrac{2}{7}\) = - \(\dfrac{11}{8}\)
\(x\) = - \(\dfrac{11}{8}\) \(\times\) \(\dfrac{2}{7}\)
\(x\) = - \(\dfrac{11}{28}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{8}{7}:x=\frac{16}{15}\)
\(x=\frac{8}{7}:\frac{16}{15}\)
\(x=\frac{15}{14}\)
\(\frac{8}{7}:X=\frac{16}{15}\)
x = \(\frac{16}{15}x\frac{8}{7}=\frac{128}{105}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
bài 5
a)
`7/5xx15/14`
`=105/70=3/2`
b)
`8/15xx25/8`
`=200/120=5/3`
c)
`2/15xx5/22`
`=10/330`
`=1/33`
bài 6
chiều rộng cx là đơn vị m phải ko ạ?
diện tích căn phòng là
`11/2xx7/2=77/4(m^2)`
\(\left(x+15\right)\div8=7\)
\(\Leftrightarrow x+15=7\times8\)
\(\Leftrightarrow x+15=56\)
\(\Leftrightarrow x=56-15\)
\(\Leftrightarrow x=41\)
Keuka