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a) x - 120: 30 = 40
x -40 =40
x =40+40
x =80
b) (x + 120) : 20 = 8
(x+ 120) = 8x20
x+120 =160
x = 160-120
x = 40
c) (x + 5). 3 = 300
x+5=300:3
x+5=100
x=100-5
x=95
d) x.2 + 21 : 3= 27
x.2 +7=27
x.2 = 27-7
x.2= 20
x=20:2
x=10
![](https://rs.olm.vn/images/avt/0.png?1311)
a, 117 - \(x\) = 28 - (-7)
117 - \(x\) = 28 + 7
117 - \(x\) = 35
\(x\) = 117 - 35
\(x\) = 82
b, \(x\) - (-38 - 2\(x\)) = (-3) - 8 + 2\(x\)
\(x\) + 38 + 2\(x\) = - 11 + 2\(x\)
3\(x\) + 38 = - 11 + 2\(x\)
3\(x\) - 2\(x\) = - 11 - 38
\(x\) = - 49
![](https://rs.olm.vn/images/avt/0.png?1311)
Bội chung nhỏ nhất của 8 ; 18 ; 30 là:
A.1080
B.120
C. 360
D.Một kết quả khác
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 16: Bội chung nhỏ nhất của 8 ; 18 ; 30 là:
A.1080
B.120
C. 360
D.Một kết quả khác
![](https://rs.olm.vn/images/avt/0.png?1311)
4. ( x - 250 ) : 6 = 64 - 12
( x- 250 ) : 6 = 52
x - 250 = 312
x = 562
5. 10x = 1030
=> x = 103
6. 30x = 120
x = 4
7. \(x=2023\)
\(8.165-\left(35:x+3\right).19=13\)
\(\left(35:x+3\right).19=152\)
\(35:x+3=8\)
\(35:x=5\)
\(x=7\)
4) \(\left(x-250\right)\div6=4^3-2^2\times3\)
\(\left(x-250\right)\div6=64-4\times3\)
\(\left(x-250\right)\div6=64-12=52\)
\(x-250=52\times6=312\)
\(x=312+250\)
\(x=562\)
5) \(2x+3x+5x=1030\)
\(x\left(2+3+5\right)=1030\)
\(10x=1030\)
\(x=1030\div10\)
\(x=103\)
6) \(15x-35x+50x=120\)
\(x\left(15-35+50\right)=120\)
\(30x=120\)
\(x=120\div30\)
\(x=4\)
7) \(\dfrac{1}{2}x+\dfrac{1}{6}x+\dfrac{1}{3}x=2023\)
\(x\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}\right)=2023\)
\(x\times1=2023\)
\(x=2023\)
8) \(165-\left(35\div x+3\right)\times19=13\)
\(\left(35\div x+3\right)\times19=165-13\)
\(\left(35\div x+3\right)\times19=152\)
\(35\div x+3=152\div19=8\)
\(35\div x=8-3=5\)
\(x=35\div5\)
\(x=7\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: =>x+38+2x=-3-8+2x
=>3x+38=2x-11
=>x=-49
b: \(\Leftrightarrow65+x-15-5x=12-5x\)
=>-4x+50=-5x+12
=>x=-38
c: \(\Leftrightarrow3x+12-7x+21=-3-5x-2=-5x-5\)
=>-4x+33=-5x-5
=>x=-38
d: \(\Leftrightarrow-123+2x+23=x-120\)
=>2x-100=x-120
=>x=-20
e: =>-45+25+5x=16-x
=>5x-20=-x+16
=>6x=36
=>x=6
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(4x^3+12=120\)
=>\(4x^3=108\)
=>\(x^3=27=3^3\)
=>x=3
b: \(\left(x-4\right)^2=64\)
=>\(\left[{}\begin{matrix}x-4=8\\x-4=-8\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-4\end{matrix}\right.\)
c: (x+1)^3-2=5^2
=>\(\left(x+1\right)^3=25+2=27\)
=>x+1=3
=>x=2
d: 136-(x+5)^2=100
=>(x+5)^2=36
=>\(\left[{}\begin{matrix}x+5=6\\x+5=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=-11\end{matrix}\right.\)
e: \(4^x=16\)
=>\(4^x=4^2\)
=>x=2
f: \(7^x\cdot3-147=0\)
=>\(3\cdot7^x=147\)
=>\(7^x=49\)
=>x=2
g: \(2^{x+3}-15=17\)
=>\(2^{x+3}=32\)
=>x+3=5
=>x=2
h: \(5^{2x-4}\cdot4=10^2\)
=>\(5^{2x-4}=\dfrac{100}{4}=25\)
=>2x-4=2
=>2x=6
=>x=3
i: (32-4x)(7-x)=0
=>(4x-32)(x-7)=0
=>4(x-8)*(x-7)=0
=>(x-8)(x-7)=0
=>\(\left[{}\begin{matrix}x-8=0\\x-7=0\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=8\\x=7\end{matrix}\right.\)
k: (8-x)(10-2x)=0
=>(x-8)(x-5)=0
=>\(\left[{}\begin{matrix}x-8=0\\x-5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=5\end{matrix}\right.\)
m: \(3^x+3^{x+1}=108\)
=>\(3^x+3^x\cdot3=108\)
=>\(4\cdot3^x=108\)
=>\(3^x=27\)
=>x=3
n: \(5^{x+2}+5^{x+1}=750\)
=>\(5^x\cdot25+5^x\cdot5=750\)
=>\(5^x\cdot30=750\)
=>\(5^x=25\)
=>x=2
![](https://rs.olm.vn/images/avt/0.png?1311)
d) Ta có: \(-8+\left(-14\right)+34+\left(-12\right)\)
\(=-8-14+34-12\)
\(=-20+20\)
\(=-0\)
e) Ta có: \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)
\(=\left(-7+57\right)+\left(-20-30\right)\)
\(=50-50=0\)
f) Ta có: \(300-\left(-180\right)-120-42\)
\(=300+180-120-42\)
\(=258+60=318\)
d, Ta có : \(\left(-8\right)+\left(-14\right)+34+\left(-12\right)\)
\(=-\left(8+12\right)+34-14=-20+20=0\)
e, Ta có : \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)
\(=-\left(30+20\right)+57-7=-50+50=0\)
f, Ta có : \(300-\left(-180\right)-120-42=318\)
Ta có :
8.(30-5x)=120
30-5x=120:8
30-5x=15
5x=30-15
5x=15
x=15:5
x=3
240-40x=120
40x=240-120
40x=120
x=120:40
x=3
vậy x=3