Question

Really need some one to explain how to do these please and thank you!

Answer 1

I don't do word problems! :P

Answer 2

This might help. Put in the values.
Then: how much time between low and high tide? What fraction of a period is it? Is it half or quarter or a full period, or something else.
Next: where is the midpoint of this graph? Half-way between 12 and 52, or the _average_ of 12 and 52, right? that is the vertical shift, because if you take away the vertical shift, the midpoint moves to zero like an ordinary cosine.