Answer:
To balance the equation place a coefficient 3 in front of NH4OH in the reactants and another 3 in front of H2O.
3 NH4OH (l) + H3PO4 (aq) → (NH4)3PO4 (aq) + 3 H2O (l)
Step-by-step explanation:
To balance equations you are only allowed to change coefficients and not subscripts. You need to make sure you have the same amount of each element on both sides of the equation, sketching a table may help.