When entering coefficients to balance equations, recall that just writing the symbol implies "1." therefore, if a coefficient of "1" is required, choose "blank" for that box. balance the following equation. 2c2h2 + o2 → 4co2 + h2o plz i really need

In a balanced equation the masses on both sides of the equation should be balanced.
given equation is 
2C₂H₂ + O₂ → 4CO₂ + H₂O
in the given equation C atoms are 4 on either side therefore C is balanced.
Number of Hydrogen is 4 on left side and 2 on right side, H needs to be balanced.
Oxygen on left side is 2 and right side is 9, O too needs to be balanced.
Therefore balanced reaction is 
2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O