\(2 + 4x - 12 = 0\)
\(4x = 10\)\(x = \frac{{10}}{4}\)\(x = \frac{5}{2}\).
$MnO_4^ - \,\, + \,\,{C_2}O_4^{2 - }\,\, + \,\,{H^ + }\, \rightarrow \,\,M{n^{2 + }}\, + \,C{O_2} + \,{H_2}O$