Answer
Coordination number : 4
Oxidation number: +2
Work Step by Step
The ligands ($Br_{4}$) that surround the central metal atom $Cd$ are 4. Thus, the coordination number is 4.
Let us suppose the oxidation number of Cd is X. To find the oxidation number, we sum the known oxidation numbers and equal it to the charge on the complex.
Also,
$Na_{2}=2\times(+1)$
$Br_{4} = 4\times (-1)$
The overall charge is zero on the complex, thus:
$2\times(+1) +X + 4\times (-1)=0$
$+2+X-4=0$
$X=+4-2$
$X=+2$
Oxidation number of Cd is +2
