So for the first one it is a decomposition reaction- there is one compound breaking down into elements
on the left you have 1 Na and 1 Cl
on the right you have 1 Na and 2 Cl
add a coefficient of 2 in front of NaCl and Na so your equation looks like this...
2 NaCl = 2 Na + 1 Cl2
That way you have 2 Na on each side and 2 Cl on each side
For the second one it's a synthesis reaction- 2 elements combining into 1 compound
Add a co efficient of 4 in front of Na and a coefficient of 2 in front of Na2O so your equation looks like this...
4 Na + 1 O2 = 2 Na2O
So you have 4 Na on both sides and 2 O on both sides
