How do you balance the following reaction: #?KOH + ?H_3PO_4 -> ?K_3PO_4 + ?H_2O#?
This reaction is a bit of an idealization, inasmuch as phosphoric acid behaves as a diprotic acid in water.
A more realistic interpretation would be,
In both cases, are mass and charge conserved? If they are not, then you know that the reaction does not reflect reality.