Для a = 12:

(6a^6)^2 = (612^6)^2 = (62985984)^2 = 17915804^2 = 320175250639216

(6a^13) = 612^13 = 6618475290624 = 3704851743744

320175250639216 : 3704851743744 ≈ 86.39