What is the molar mass of mg3(po4)2, a substance formerly used in medicine as an antacid?

First let us determine the molar masses of each element.

Mg = 24.31 g/mol

P = 39.10 g/mol

O = 16 g/mol

Therefore the overall molar mass is:

molar mass = 3 * (24.31 g/mol) + 2 (39.10 g/mol) + 8 (16 g/mol)

molar mass = 279.13 g/mol

the answer is 75.0%.