if x=log(75,45) and y=log(375,135).

find xy+5(x-y)

What representation of log function is this?

Proceeding with assumption:
I am assuming that one of the numbers is the base of log and other is the variable.
You can proceed by using base transformation formulae. Take the base as a common factor between the base number and the variable which should give you same composition of log function which inturn can be taken to be a variable(just for convenience sake) and proceed with combining them to get the desired results for xy+5(x-y).