i would like to ask for your help with these two problems :

I've got the answers i'm just not quite sure how to get to those answers.I've got the basic knowledge in analog electronics i just have a difficult time putting it all together.I would like to know if there are any things in particular to watch out for when dealing with these kinds of problems or better yet if there's any kind of a general algorithm i should follow when solving them.

I guess the bottom line is how do i go about solving this ?

Thank you for your help.

Ondroid.