In this equation, we have the following electron transfers:

P2O5 + C --> P + CO2

The oxidation states of each element are as follows:

Phosphorus $P$ in P2O5 is in the +5 oxidation state.Carbon $C$ in C is in the 0 oxidation state.Phosphorus $P$ in P is in the +3 oxidation state.Carbon $C$ in CO2 is in the +4 oxidation state.

To balance the electron transfer in this reaction, we need to ensure that the number of electrons lost by the reducing agent $C$ is equal to the number of electrons gained by the oxidizing agent $P2O5$.

We start by writing the half-reactions for each element:
Oxidation: C --> CO2 $loses4electrons$ Reduction: P2O5 --> P $gains2electrons$

To balance the electron transfer, we need to multiply the reduction half-reaction by 2 and the oxidation half-reaction by 4 to equalize the number of electrons exchanged.

4C --> 4CO2 $loses16electrons$ 2P2O5 --> 4P + 5O2 $gains4electrons$

Now the electron transfer is balanced, with C losing 16 electrons and P2O5 gaining 16 electrons.