The mass of sodium present in 5.85 g of $\mathit{NaCl}$ is:

The mass of sodium present in $5.85\mathit{ g}$ of $\mathit{NaCl}$ is $2.3\mathit{ g}$.
Mass of $\mathit{NaCl}$ = 5.85g
Molar mass of $\mathit{NaCl}$ = 58.5 $\frac{g}{\mathit{mol}}$
⇒So 5.85g of  $\mathit{NaCl}$ contains = $\frac{5.85}{58.5}\times 23$
$=2.3g$ of sodium.
Therefore, there are 2.3g of Na present in 5.85g of $\mathit{NaCl}$.