53.5 g MgCl2 /95.21 g/mol = 0.5619 Moles MgCl2. Since the ratio is 3MgCl : 2Na3PO4 you multiply 0.5619 x 2/3 (since you're solving for NaPO, the 2 goes on top) which shows we have .3746 Moles of NaPO. Multiply times it's molar mass so 0.3746x 163.94g/mol= 61.4136 grams NaPO. I believe.