Using the properties
and
, we have
2 log₅ (5x³) + 1/3 log₅ (x² + 6)
= log₅ (5x³)² + log₅ ∛(x² + 6)
= log₅ (25x⁶) + log₅ ∛(x² + 6)
= log₅ (25x⁶ ∛(x² + 6))
Trying to parse the choices you listed is ... difficult. I trust you'll be able to figure out which one matches best on your end.