The total number of unpaired electrons present in the complex  $K_3\left[Cr{\left(oxalate\right)}_3\right]$ is ….

Let oxidation state of Cr is x
$3(+1)+x+3(-2)=0$
$x=+3$
Cr electronic configuration is 24
$\left[Ar\right]3d^{5}4s^1$
$C{r}^{3+}\underset{ }{\overset{ }{\to }}\left[Ar\right]3d^3$
Unpaired electrons = 3