How to Determine the Height of an Object Dropped at a Given Speed?

[NumberNumber]

Tim drops his watch from a 3-story-building, 12.5 m above ground. In task a. you were asked to find what the v was when it hit the ground, the answer was 15.7. However I am having trouble finding the answer to task b in which you are asked to find the h when the watch is dropped at the speed of 10 m/s.

In a I solved the equation by using
Ek = Ep

But I'm having trouble with b

 

[Dale]

What have you attempted so far with B?