How do you balance #PH_3 + O_2 -> P_4O_10 + H_2O#?
You balance this redox equation stoichiometrically.
IS this equation stoichiometrically balanced; that is for every reactant particle, is there a corresponding product particle?
Combustion reactions like these can usually be balanced directly, without that tedious mucking about with redox half equations. Hydrocarbon combustion reactions might be balanced the same way. Note that this IS FORMALLY a redox reaction: