Convert the g NaCl to moles, multiply by 3/2 and then divide by the molecular weight of oxygen.
The equation shows that for every 2 moles of NaCl produced, it will produce 3 moles of oxygen. So, by converting the given amount of NaCl grams to moles of NaCl, you can use the equation to find out how many moles of oxygen must have been produced. That ratio is 3:2. Once you have that value you can convert it back from moles to grams of Oxygen using the molecular weight of oxygen (32 in this case, not 16, as the equation uses the diatomic form).