Given mass of compounds =681g
Molar mass of C7H5N3O6=12×7+5×1+14×3+6×16
=84+5+42+96
=227
Number of moles of compound =227681=3 moles
Number of moles of N=3×number of moles of compound
=3×3=9 moles
Number of atoms of N =9×6.02×1023
=5418×1021
So x=5418