Hi, I have a question about this problem. I haven't looked through the others yet, but I have a question on this one specifically because I thought this was the correct answer, and now I am confused. I thought it was only 3. The answer that it said was 1 and 3 only, not 3 only. How?

I am pretty sure that both 1 and 3 are balanced, because:

Equation #1:
Left side of equation      Right side of equation
4 N                    =   4 N
4x3 = 12, so 12 H      =   6x2 = 12, so 12 H         
5x2 = 10, so 10 O      =   4 O, but +6 for the other O's, so 10 O
So the first equation is balanced, as well as the 3rd.

oh, I didn't see the other O's thank you Avni