To calculate this expression, we need to use the properties of logarithms.

First, we simplify the expression:
log3 60 - log3 0.75

Then, we use the property of logarithms that states log_a(x) - log_a(y) = log_a(x/y):
log3 (60/0.75)

Next, we simplify the expression further by dividing 60 by 0.75:
log3 80

Therefore, log3 60 - log3 0.75 is equal to log3 80.