given 6.7 grams of sodium acetate and 6.7 g of magnesium acetate, calculate the number of moles of acetate in sodium acetate. calculate the number of moles of acetate in magnesium acetate.

moles = grams/molar mass

moles Ac in NaAc = grams/molar mass.

In Mg(Ac)2, it is
moles Mg(Ac)2 = moles/molar mass.
Since there are two moles Ac in 1 mole Mg(Ac)2, then moles Ac^- must be twice that.