Hi Widodoi,
Assuming loga48 - loga3 is the numerator and loga2 is the denominator, you are missing some punctuation. Since the difference of two logs is equal to the log of a quotient, loga48 - loga3 can be written as loga(48/3) or loga16, then (loga48 - loga3)/loga2 = (loga16)/loga2 = (loga24)/loga2. Using the power rule loga24 = 4loga2, so (loga24)/loga2 = (4loga2)/loga2. Now divide out the common factor of loga2 from the numerator and the denominator so that 4loga2/loga2 = 4