Write the expression below as a single log.
2log_3(u) - log_3(v)
He assumed that you already know the properties of logarithms, which he posted not a long time ago in a previous thread of yours.
When you have a difference between two logs, the two logs can be combined in one log of a quotient. The numerator contains the inside terms of the positive log and the denominator consists of the inside terms of the negative log.