\(\left(19-x:2\right)\inƯ\left(13\right)=\left\{1;13\right\}\)
\(=>\left[{}\begin{matrix}19-x:2=1\\19-x:2=13\end{matrix}\right.\)
\(=>\left[{}\begin{matrix}x=36\\x=12\end{matrix}\right.\)

\(\Leftrightarrow x-3\in\left\{1;-1;17\right\}\)

hay \(x\in\left\{4;2;20\right\}\)

\(\left(x-3\right)\inƯ\left(17\right)=\left\{1;17\right\}\)
\(=>\left[{}\begin{matrix}x=4\\x=20\end{matrix}\right.\)

\(x⋮24\\ x⋮40\\ x⋮168\\ \Rightarrow x⋮BCNN\left(24;40;168\right)\\ \Rightarrow x⋮840\\ \Rightarrow x\in B\left(840\right)=\left\{0;840;...\right\}\)

Do \(x< 250\Rightarrow x=0\)

-x-6=-10

-x=(-10)+6

-x=-4

x=4

7-x=-5

x=7-(-5)

x=2

-x-6=-10

-x   =-10+6

-x   =4

x    =-4

7-x=-5

-x  =-5-7

-x  =-12

x   =12

-x-18=-23

-x=-5

x=5

⇔(-18)-x=-23

⇔x=5

\(-18-x=-9+\left(-14\right)\\ \Rightarrow-18-x=-23\\ \Rightarrow x=-18-\left(-23\right)\\ \Rightarrow x=41\)

⇔x-10=-48

⇔x=(-48)+10

⇔x=-38

x + (-10) = (-48)
x = (-48) - (-10)
x = -38

x=-38

\(\left(3x-2^4\right).7^3=2.7^4\)

\(\left(3x-2^4\right)=2.7^4:7^3\)

\(\left(3x-2^4\right)=2.7\)

\(\left(3x-2^4\right)=14\)

\(3x-16=14\)

3x=16+14

3x=30

x=30:3

x=10

(4+10)x4:2=28