Answer:
• 2,1,2
Explanation:
aMg +b O2 --> cMgO
Rule of balancing :- Number of atom of an element should be equal on both side of equation.
Balancing O :- 2b = c
( now by hit and trial method )
for b = 1 => c = 2
and Balancing Mg :-
c= 2 and c = a
=> a = 2