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Q(a) Find the value of x in the following :

         (i) $\left[x 7\right]\left[\begin{array}{c}4\\ x\end{array}\right]=\left[22\right]$


    (b). If [2x  4 ] = $\left[\begin{array}{c}x\\ -8\end{array}\right]$, find the positive value of x.