pH = pKa + log([A-]/[HA])
You know pH, you know pKa, the only thing left is the ratio of dissociated acid with nondissociated acid. Run it once for ammonia and once for the phosphoric acid. Once you know what the log term is, you can determine whether the ratio is greater than or less than one, which tells you whether the dissociated form or the undissociated form of the species predominates.
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