Ta có: $\left|x-3\right|=\left|4-x\right|\Rightarrow [\begin{array}{c}x-3=4-x\\ x-3=x-4\end{array}\Rightarrow [\begin{array}{c}x+x=4+3\\ x-x=-4+3\end{array}$

$\Rightarrow [\begin{array}{c}2x=7\\ 0x=-1\end{array}\Rightarrow [\begin{array}{c}x=3,5\left(TM\right)\\ 0x=-1\left(loại\right)\end{array}$

Vậy x=3,5

Ta có: $\left|x-3\right|=\left|4-x\right|\Rightarrow [\begin{array}{c}x-3=4-x\\ x-3=x-4\end{array}\Rightarrow [\begin{array}{c}x+x=4+3\\ x-x=-4+3\end{array}$

$\Rightarrow [\begin{array}{c}2x=7\\ 0x=-1\end{array}\Rightarrow [\begin{array}{c}x=3,5\left(TM\right)\\ 0x=-1\left(loại\right)\end{array}$

Vậy x=3,5

Ta có: $\left|x-3\right|=\left|4-x\right|\Rightarrow [\begin{array}{c}x-3=4-x\\ x-3=x-4\end{array}\Rightarrow [\begin{array}{c}x+x=4+3\\ x-x=-4+3\end{array}$

$\Rightarrow [\begin{array}{c}2x=7\\ 0x=-1\end{array}\Rightarrow [\begin{array}{c}x=3,5\left(TM\right)\\ 0x=-1\left(loại\right)\end{array}$

Vậy x=3,5

Tạo ra 5 mã số khác nhau là $135,153,315,351,513,531$.