What have you got so far?
The first one I would draw a diagram to help you conceptualize what the question is asking. Do you know what an absolute value is?
The second one you're just plugging in for H and solving for time (you will get an extraneous solution; see if you can find which one it is).
The third one asks you to understand the properties of radicals such as:
On the fourth one, you will have to multiple by a conjugate. Are you familiar with conjugates. I would imagine so if they are asking you to get the radical out of the denominated. The conjugate of is .
On the fifth, simply a matter of rearranging the equation, expanding the square and solving for zero.