I'll do the first one for you and explain why I got the answer I got. So, we are given the following:

And for the first question we are given:

This is not neccesarily true. Heres why; consider the following property of numbers which are greater then zero.

Now, with the above, remember that the problem started with:

If:

Then:

Also, if:

Then:

All the above holds given that:

If problem (a) had said:

then it would be neccesarily true, since we can start with:

then get to it by:

But question (a) only said:

Does that make sense? Now, using the properties of inequalities of positive numbers, see if you can't figure out the other questions. If your still stuck, post here and I'll give you more assitance