Tìm x biết : a) x*3,1+x*6,9=30,4 b) x:1,5+0,45=7,65
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a) 1,26 : x + 2,34 : x =5
\(1,26\times\frac{1}{x}+2,34\times\frac{1}{x}=5\)
\(\frac{1}{x}\times\left(1,26+2,34\right)=5\)
\(\frac{1}{x}\times3,6=5\)
\(\frac{1}{x}=5:3,6\)
\(\frac{1}{x}=\frac{18}{25}\)
\(x=\frac{25}{18}\)
b) \(x\times3,1+x\times6,9=30,4\)
\(x\times\left(3,1+6,9\right)=30,4\)
\(x\times10=30,4\)
\(x=30,4:10\)
\(x=3,04\)
c) \(x:1,5+0,45=7,65\)
\(x:1,5=7,65-0,45\)
\(x:1,5=7,2\)
\(x=1,5\times7,2\)
\(x=11,1\)
Chúc bn học tốt !
![](https://rs.olm.vn/images/avt/0.png?1311)
a/ => X. (3,1+6,9)=25
=> X.10=25
=> X=25:10=5/2
b/ X.3 = 7,65-31,5.0,1
=> 3X=4,5
=> X=4,5:3 = 1,5
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x.3,1+x.6,9+5,4=30,4\)
\(x.\left(3,1+6,9\right)+5,4=30,4\)
\(x.10+5,4=30,4\)
\(x.10=30,4-5,4\)
\(x.10=25\)
\(x=25\div10\)
\(x=\frac{5}{2}\)
b) \(31,5.0,1+x.3=7,65\)
\(3,15+x.3=7,65\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,x\times3,1+x\times6,9+5,4=30,4\)
\(x\times3,1+x\times6,9=30,4+5,4\)
\(x\times3,1+x\times6,9=35,8\)
\(x\times\left(3,1+6,9\right)=35,8\)
\(x\times10=35,8\)
\(x=35,8:10\)
\(x=3,58\)
![](https://rs.olm.vn/images/avt/0.png?1311)
x.3,1+x.6,9+5,4=30,4
=> x.(3,1+6,9)+5,4=30,4
=> x.10 =30,4-5,4
=> x.10 =25
=> x =25:10
=> x =2,5
Vậy x=2,5
X x 3,1 + X x 6,9 + 5,4 = 30,4
X x(3,1+6,9) + 5,4 =30,4
X x 10 +5,4 = 30,4
X x 10= 30,4 - 5,4
X x 10=25
X=25:10
X= 2,5
![](https://rs.olm.vn/images/avt/0.png?1311)
X x 3,1 + X x 6,9 = 30,4
X x ( 3,1 + 6,9 ) = 30,4
X x 10 = 30,4
X = 30,4 : 10
X = 3,04
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(x:1,5\right)+0,45=7,65\)
=>\(x:1,5=7,65-0,45\)
=>\(x:1,5=7,2\)
=>\(x=7,2\times1,5\)
=>\(x=10,8\)
Vậy x = 10,8
a, Xx3,1+Xx6,9=30,4
Xx(3,1+6,9)=30,4
Xx10=30,4
X=30,4:10
x=3,04
x=3,04