( 14 - x : 6 ) x 7 = 84

14 - x : 6 = 84 : 7

14 - x : 6 = 12

x : 6 = 14 - 12

x : 6 = 2

     x = 2 x 6

     x = 12

( 14 - x : 6 ) x 7 = 84

14 - x : 6 = 84 : 7

14 - x : 6 = 12

x : 6 = 14 - 12

x : 6 = 2

     x = 2 x 6

     x = 12

( 14 - x : 6 ) x 7 = 84

14 - x : 6 = 84 : 7

14 - x : 6 = 12

x : 6 = 14 - 12

x : 6 = 2

     x = 2 x 6

     x = 12

14 - x:6 = 84:7

14 - x:6=12

x:6=14-12

x:6=2

x=2x6

x=12

14-x:6= 84:7 =12

x:6=12+14=26

x= ...??

    (14-x:6).7=84

=>14-x:6     =84:7=12

=>x:6          =14-12=2

=>x             =2.6=12

vậy x=12

dúng đó k nha 

a)0,12.X-2=4

=>0,12.X=4+2

=>0,12.X=6

=>X=6:0,12

=>X=50

b)231-(X-6)=1339:13

=>231-(X-6)=103

=>X-6=231-103

=>X-6=128

=>X=128+6

=>X=134

c)7,99.X+X.2+X:100=7,9

=>X.(7,99+2+1/100)=7,9

=>X.10=7,9

=>X=7,9:10

=>X=0,79

d)(14-X:6).7=84

=>14-X:6=84:7

=>14-X:6=12

=>X:6=14-12

=>X:6=2

=>X=2.6

=>X=12

a,   -14 - 7 + x = -12

    \(\Leftrightarrow-21+x=-12\)

    \(\Leftrightarrow x=-12+21\)

    \(\Leftrightarrow x=9\)

b,    \(x+\left(-15\right)-\left(-6\right)=11\)

\(\Leftrightarrow x-15+6=11\)

\(\Leftrightarrow x-\left(15-6\right)=11\)

\(\Leftrightarrow x-9=11\)

\(\Leftrightarrow x=11+9\)

\(\Leftrightarrow x=20\)

 c,   \(x-\left[18+\left(-7\right)\right]=15\)

\(\Leftrightarrow x-\left(18-7\right)=15\)

\(\Leftrightarrow x-11=15\)

\(\Leftrightarrow x=15+11\)

\(\Leftrightarrow x=26\)     

d,   \(-84-\left(-18-6\right)=x+\left(-20\right)\)

\(\Leftrightarrow-84-\left(-24\right)=x+\left(-20\right)\)

\(\Leftrightarrow-84+24=x+\left(-20\right)\)

\(\Leftrightarrow-60=x+\left(-20\right)\)

\(\Leftrightarrow x=-20+60\) 

\(\Leftrightarrow x=40\)

a) \(\dfrac{3}{4}\times x:\dfrac{1}{2}=\dfrac{4}{5}\)

\(\dfrac{3}{4}\times x=\dfrac{4}{5}\times\dfrac{1}{2}\)

\(\dfrac{3}{4}\times x=\dfrac{2}{5}\)

\(x=\dfrac{2}{5}:\dfrac{3}{4}\)

\(x=\dfrac{8}{15}\)

b) \(\left(14-x:6\right)\times7=84\)

\(14-x:6=84:7\)

\(14-x:6=12\)

\(x:6=14-12\)

\(x:6=2\)

\(x=6\times2=12\)

c) \(x\times1,5:2,4=0,3\)

\(x\times1,5=0,3\times2,4\)

\(x\times1,5=0,72\)

\(x=0,72:1,5\)

\(x=0,48\)

d) Thiếu x

( 14 - x : 6 ) * 7 = 84

( 14 - x : 6 )      = 84 : 7

( 14 - x : 6 )      = 12

14 - x : 6 = 12

14 - x = 12 : 6    

14 - x = 2

       x =14 - 2

        x = 12

Nhớ k cho mk nha !!!!!!!!!!! 

( 14 - x : 6 ) x 7 = 84

( 14 - x : 6 ) = 84 : 7

( 14 - x : 6 ) = 12

14 - x : 6 = 12

14 - x = 12 : 6

14 - x = 2

x = 14 - 2

x = 12

Vậy x = 12

( 14 - x : 6 ) x 7 = 84

( 14 - x : 6 ) = 84 : 7

( 14 - x : 6 ) = 12

14 - x : 6 = 12

14 - x = 12 : 6

14 - x = 2

x = 14 - 2

x = 12