write in the form of logA:

log2 + log12

3log5 + 2log3

1/4log81

log36 - log12

log 2 + log 12 = log (2*12) = log 24

3log5 + 2log3 = log (5^3*3^2)= log 1125
(1/4)log 81 = log 81^(1/4) = log 3

You do the last one.
Remember log a - log b = log a/b