a) -15÷x=3

            x=-15÷3

           x=-5

b) -3x+8=-7

    -3x .   =-15

       x.     =-15÷-3

      x.      = 5

c) ( x-6) (7- x) =0

Suy ra: * x-6 =0=) x=6

             *7-x=0=) x=7

Vậy x=6;7

a, -15:x=3

\(\Rightarrow x=-15:3\)

\(\Rightarrow x=-5\)

Vậy x=-5

b,-3x+8=-7

\(\Rightarrow-3x=-7-8\)

\(\Rightarrow-3x=15\)

\(\Rightarrow x=15:\left(-3\right)\)

\(\Rightarrow x=5\)

Vậy x=5

c, (x-6)(7-x)=0

\(\Rightarrow\orbr{\begin{cases}x-6=0\\7-x=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0+6\\x=7-0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=6\\x=7\end{cases}}\)

Vậy \(\orbr{\begin{cases}x=6\\x=7\end{cases}}\)

a. -6x=18

\(\Rightarrow x=18:\left(-6\right)\)

\(\Rightarrow x=-3\)

Vậy x=-3

b,2x-(-3)=7

\(\Rightarrow2x=7+\left(-3\right)\)

\(\Rightarrow2x=4\)

\(\Rightarrow x=4:2\)

\(\Rightarrow x=2\)

Vậy x=2

c,(x-5)(x+6)=0

\(\Rightarrow\orbr{\begin{cases}x-5=0\\x+6=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0+5\\x=0-6\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=5\\x=-6\end{cases}}\)

Vậy \(\orbr{\begin{cases}x=5\\x=-6\end{cases}}\)

- 6x = 18

x = 18 : ( - 6 )

x = -  3

a, 7\(x\).(2\(x\) + 10) =0

    \(\left[{}\begin{matrix}x=0\\2x+10=0\end{matrix}\right.\)

    \(\left[{}\begin{matrix}x=0\\2x=-10\end{matrix}\right.\)

     \(\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\)

Vậy \(x\in\) {-5; 0}

b, -9\(x\) : (2\(x\) - 10) = 0

    9\(x\)                   = 0 

     \(x\)                    = 0 

c, (4 - \(x\)).(\(x\) + 3)  = 0

    \(\left[{}\begin{matrix}4-x=0\\x+3=0\end{matrix}\right.\)

    \(\left[{}\begin{matrix}x=4\\x=-3\end{matrix}\right.\)

Vậy \(x\in\) {-3; 4}

mình ko biết

I/ x=0

b ) 3 - ( x - 5 ) = - 7 + ( - 8 )

     3 - ( x - 5 ) = - 15

            x - 5   = 3 - ( - 15 )

            x - 5   = 18

                 x   = 18 + 5

                 x   = 23

Vậy x = 23

nhớ giải luôn nha bạn

\(a,x-\frac{3}{4}=\frac{1}{7}\)

\(x=\frac{1}{7}+\frac{3}{4}=\frac{25}{28}\)

\(b,\frac{15}{x}-\frac{1}{3}=\frac{28}{51}\)

\(\frac{15}{x}=\frac{28}{51}-\frac{1}{3}=\frac{15}{17}\)

\(\Rightarrow x=17\)

học tốt ~~~

\(x-\frac{3}{4}=\frac{1}{7}\)

\(x\)          \(=\frac{1}{7}+\frac{3}{4}\)

\(x\)          \(=\frac{4}{28}+\frac{21}{28}\)

\(x\)           \(=\frac{4+21}{28}\)

\(x\)             \(=\frac{25}{28}\)