Answer : The coefficient of sulfuric acid is, 3 and the balanced chemical reaction will be,

Explanation :
Balanced chemical equation : It is defined as the number of atoms of individual elements present on reactant side always be equal to the product side.
The balanced chemical reaction will be,
By the stoichiometry we can say that, 1 mole of magnesium phosphate react with 3 moles of sulfuric acid to give 3 moles of magnesium sulfate and 2 moles of phosphoric acid.
The coefficient of magnesium phosphate = 1
The coefficient of sulfuric acid = 3
The coefficient of magnesium sulfate = 3
The coefficient of phosphoric acid = 2