The oxidation numbers of sulfur (S) chromium (Cr) and nitrogen (N) in ${\mathrm{H}}_2{\mathrm{SO}}_5$, ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$ and ${\mathrm{NO}}_3^{-}$ are respectively

${\mathrm{H}}_2{\mathrm{SO}}_5$ - peroxy monosulphuric acid / caros acid $2\left(+1\right)+1\left(\mathrm{S}\right)+3\left(-2\right)+2\left(-1\right)=0\Rightarrow \mathrm{S}=+6$

Dichromate ion ${\mathrm{Cr}}_2{\mathrm{O}}_7^{-2}$

$2\left(\mathrm{Cr}\right)+7\left(-2\right)=-2\Rightarrow \mathrm{Cr}=+6$

Nitrate ion ${\mathrm{NO}}_3^{-}$ ; $1\left(\mathrm{N}\right)+3\left(-2\right)=-1\Rightarrow \mathrm{N}=+5$