What is the oxidation number of sulphur in $SO_3$?

Oxidation state of manganese in potassium permanganate is:

The oxidation state of sulfur in the anions $SO_3^{2-}$,$S_2O_4^{2-}$,and $S_2O_6^{2-}$ increases in the order:

When $KMnO_4$ is reduced with oxalic acid in acidic solution,the oxidation number of $Mn$ changes from

Assign the oxidation number to the underlined element in each of the following species:
$1$. $K_2\underline{Mn}O_4$
$2$. $Ca\underline{O}_2$
$3$. $Na\underline{B}H_4$
$4$. $KAl(\underline{S}O_4)_2 \cdot 12H_2O$

What is the change in oxidation number of nitrogen in the following conversion? $NO_3^{-} \longrightarrow NO_2$