We can write 7.2 as 6*6/5

log 7.2 = log 6*6 / 5 = log 6^2 / 5

Now log (a^b) = b* log a and log (a/b) = log a - log b

log (6^2 / 5)

=> 2 log 6 - log 5

as log 6 = m and log 5 = n

=> 2m - n

**Therefore log 7.2 = 2m - n**

We can write 7.2 as 6*6/5

log 7.2 = log 6*6 / 5 = log 6^2 / 5

Now log (a^b) = b* log a and log (a/b) = log a - log b

log (6^2 / 5)

=> 2 log 6 - log 5

as log 6 = m and log 5 = n

=> 2m - n

**Therefore log 7.2 = 2m - n**