A stone thrown vertically upward with an initial velocity of 29.4 m/s from the top of a tower 34.3m high find
[a]the time taken to reach the maximum height
[b]total time that elapsed before it reaches the ground

So let's see your work, we don't do it for you. How fast does the stone fall?

There are 3 basic relations between velocity, displacement, acceleration & time.
Just go through those equations and see which one fits with your question.
If still you have a problem, show your approach on the question so that I can see and guide you.