The third equation is properly balanced.
To figure this out, set up tables to check if each element has the same amount on both sides. If you do this for the third equation, copper, hydrogen, oxygen, and nitrogen are all balanced,
The first equation is incorrect due to the fact Iron, Fe, is not balanced on both sides. This is shown by the subscripts given.
The second equation is incorrect as Sulfur is not properly balanced and neither is sodium.
The fourth equation is incorrect as Aluminum is not properly balanced. On the reactants side, Aluminum is 4 while on the products, Aluminum is 8.
Hope this helps!
