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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
\(1440:\left[120-\left(3.9x\right)\right]=120\) \(120+\left[\left(999-9x\right):60\right].24=480\)
\(120-\left(3.9x\right)=1440:120\) \(\left[\left(999-9x\right):60\right].24=360\)
\(120-\left(3.9x\right)=12\) \(\left(999-9x\right):60=15\)
\(3.9x=120-12\) \(999-9x=900\)
\(3.9x=108\) \(9x=999-900\)
\(9x=108:3\) \(9x=99\)
\(9x=36\) \(x=99:9\)
\(x=4\) \(x=11\)
\(\dfrac{1}{120}\cdot120+x:\dfrac{1}{3}=-4\)
\(\Leftrightarrow1+x\cdot3=-4\)
\(\Leftrightarrow3x=-5\)
\(\Leftrightarrow x=-\dfrac{5}{3}\)
\(\dfrac{1}{120}.120+x:\dfrac{1}{3}=-4\)
\(1+x:\dfrac{1}{3}=-4\)
\(x:\dfrac{1}{3}=-4-1\)
\(x:\dfrac{1}{3}=-5\)
\(x=-5.\dfrac{1}{3}\)
\(x=\dfrac{-5}{3}\)
a. 1440 : [ 120 - (3x + 9 ) ] = 120
120 - (3x + 9) = 1440 : 120 = 12
3x + 9 = 120 - 12 = 108
3x = 108 - 9 = 99
x = 99 : 3 = 33
b. 120 + [ ( 999 - 9x ) : 60 ] . 24 = 480
[ ( 999 - 9x ) : 60 ] . 24 = 480 - 120 = 360
( 999 - 9x ) : 60 = 360 : 24 = 15
( 999 - 9x ) = 15 . 60 = 900
9x = 999 - 900 = 99
x = 99 : 9 = 11
\(\left[3\cdot\left(x+2\right):7\right]\cdot4=120\)
\(\Rightarrow3\left(x+2\right):7=30\)
\(\Rightarrow3\left(x+2\right)=210\)
\(\Rightarrow x+2=70\)
\(\Rightarrow x=68\)
Vậy x=68
[ 3 . ( x + 2 ) : 7 ] . 4 = 120
3 . ( x + 2 ) : 7 = 30
3 . ( x + 2 ) = 210
x + 2 = 70
x = 68
Nhớ li ke mk nha
( 3 x ( x + 2 ) : 7 ) x 4 = 120
( 3 x ( x + 2 ) : 7 ) = 120 : 4
3 x ( x + 2 ) : 7 = 30
3 x ( x + 2 ) = 30 x 7
3 x ( x +2 ) = 210
x + 2 = 210 : 3
x + 2 = 70
x = 68
\(1+2+3+4+...+x=120\)
\(\Rightarrow\frac{\left(x+1\right).x}{2}=120\)
\(\Rightarrow\left(x+1\right).x=120.2\)
\(\Rightarrow\left(x+1\right).x=240\)
\(\Rightarrow\left(x+1\right).x=16.15\)
\(\Rightarrow x=15\)
\(\frac{120}{1,2x}+\frac{2}{3}=\frac{120}{x}\Rightarrow\frac{100}{x}+\frac{2}{3}=\frac{120}{x}\)
\(\Rightarrow\frac{20}{x}=\frac{2}{3}\Rightarrow x=\frac{20.3}{2}=30\)
120/1.2x+2/3=120/x
100/x-120/x=-2/3
-20/x=-2/3
x=30