c
(c) $2X - \left[ {\begin{array}{*{20}{c}}1&2\\7&4\end{array}} \right]\, = \,\left[ {\begin{array}{*{20}{c}}3&2\\0&{ - 2}\end{array}} \right]$
==> $2X = \left[ {\begin{array}{*{20}{c}}3&2\\0&{ - 2}\end{array}} \right] + \left[ {\begin{array}{*{20}{c}}1&2\\7&4\end{array}} \right]$
==> $2X = \left[ {\begin{array}{*{20}{c}}4&4\\7&2\end{array}} \right]$
==> $X = \left[ {\begin{array}{*{20}{c}}2&2\\{7/2}&1\end{array}} \right]$.