\(\left(Q\right):x+3y-z-2=0\Rightarrow\overrightarrow{n_Q}=\left(1;3;-1\right)\)
\(\left(T\right):2x+6y-2z+15=0\Rightarrow\overrightarrow{n_T}=\left(2;6;-2\right)\)
\(\Rightarrow\overrightarrow{n_T}=2\overrightarrow{n_Q}\)
\(\Rightarrow\left(Q\right)//\left(T\right)\)
\(\Rightarrow\) Chiều rộng của bức tường \(\left(Q\right)\) là :
\(d\left(\left(Q\right);\left(T\right)\right)=\dfrac{\left|\dfrac{15}{2}+2\right|}{\sqrt{1^2+3^2+\left(-1\right)^2}}=\dfrac{\dfrac{19}{2}}{\sqrt{11}}=\dfrac{19\sqrt{11}}{22}\approx2,86\left(m\right)\)