I'm curious as to how the answers for these came up.

For problem 1, given that log2 7 is approximately equal to 2.8074, find an approximation for each logarithm. Solve log2 3 square root of 7.

For problem 2, given that log2 5 is approximately equal to 2.3219, find an approximation for each logartihm.

http://img810.imageshack.us/img810/8651/logw.th.png

If anyone could shed some light on these problems, I dont understand how in problem 1 in the solution is not the sum of two logarithms like in problem 2, and how in problem 1 uses multiplication and problem 2 uses addition. I just need a bit of guidance, i'm a highschool student and I would like to understand this for upcoming exams.