Solve each of the following matrix equations without a calculator.  

1. $\left[ \begin{array} { c c } { 5 } & { 10 } \\ { - 6 } & { 4 } \end{array} \right] X + \left[ \begin{array} { c } { - 1 } \\ { 2 } \end{array} \right] = \left[ \begin{array} { c } { - 6 } \\ { 4 } \end{array} \right]$ 

    Step (a):

   $\left[ \begin{array} { c c } { 5 } & { 10 } \\ { - 6 } & { 4 } \end{array} \right] X = \left[ \begin{array} { c } { -6 } \\ { 4 } \end{array} \right] = \left[ \begin{array} { c } { -1 } \\ { 2 } \end{array} \right]$

2. $\left[ \begin{array} { c c } { 8 } & { - 1 } \\ { 4 } & { - 7 } \end{array} \right] Y = \left[ \begin{array} { c c } { 8 } & { - 54 } \\ { 4 } & { - 14 } \end{array} \right]$ 

   Hint (b):

   If $AY = B$, then $Y = A^{−1}B$.