In structure $(13)$ there is a pair of electrons at $C_3$ and double bonds at $C_4-C_5$ and $C_1-C_2.$ The unshared

pair at $C_3$ is pushed toward $C_4$ and the pair of pi electrons at $C_4-C_5$ is pushed toward $C_5.$

This process can be repeated twice more to generate equivalent, but not identical, structures.

$(15)$

$(16)$

A similar operation on $(16)$ regenerates $(12).$

There are five acceptable resonance structures for the benzyl cation.