Answer:
Sum of coefficients in balanced equation is 18
Explanation:
Unbalanced equation: [tex]Mg_{3}(PO_{4})_{2}+C\rightarrow Mg_{3}P_{2}+CO[/tex]
Balance O: [tex]Mg_{3}(PO_{4})_{2}+C\rightarrow Mg_{3}P_{2}+8CO[/tex]
Balance C: [tex]Mg_{3}(PO_{4})_{2}+8C\rightarrow Mg_{3}P_{2}+8CO[/tex]
Balanced equation:[tex]Mg_{3}(PO_{4})_{2}+8C\rightarrow Mg_{3}P_{2}+8CO[/tex]
Sum of coefficients in balanced equation = (1+8+1+8) = 18
So, option (4) is correct.