Average of 13 results is 65

Average of 13 results is 65. If the average of first six results is 61 and average of last six results is 59 Then find the seventh result?

Its source gives only the correct option, without the working.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #23811