\(i.e.,\,\,\,X + 2\left( { + 1} \right) + 2\left( { - 1} \right) = 0\)
\(\therefore X = 0\)
$14{H^ + } + C{r_2}O_7^{2 - } + 3Ni \to 2C{r^{3 + }} + 7{H_2}O + 3N{i^{2 + }}$