Mass of sodium chloride (NaCl) = 12.5 g

Molar mass of sodium chloride (NaCl) = 23 + 35.5 = 58.5 g

$\text{Number of moles} = \frac{\text{Mass in grams}}{\text{Molar mass}}$

$\text{Number of moles} = \frac{12.5}{58.5}$

$\text{Number of moles} = 0.21 \text{ moles}$