An important rule of logs is a*log b = log b^a.
Thus, 2 (log to the base 5 of )(5x^3) = (log to the base 5 of ) (5x^3)^2, or
(log to the base 5 of ) (25x^6).
Next, (1/3) (log to the base 5 of ) (x^2+6) = (log to the base 5 of ) (x^2+6)^(1/3).
Here, the addition in the middle of the given expression indicates multiplication:
2Log5(5x^3)+1/3log5(x^2+6) = (log to the base 5 of ) { (5x^3)^2 * (x^2+6)^(1/3) }.
Here we've expressed the given log quantity as a single log.