A metal forms a chloride with the formula MCl₂. Formula of Phosphoric acid is H₃PO₄. Formula of the Phosphate of the metal is

From the given data, charge on  'M' = +2

charge on Phosphate= -3

According to criss-coss method, The charge on M will become subscript of of phosphate ion and  charge on ${\mathrm{PO}}_4^{-3}$ becomes subscript of M.  

Hence, Formula of the Phosphate of the metal is ${\mathrm{M}}_2{\left({\mathrm{PO}}_4\right)}_3$.