A spring gun, held horizontally 1.70 m above the ground, fires a 0.010 kg marble so that it lands a horizontal distance of 7.60 m away. If the gun is pointed straight up, and the same marble is fired, how high (in meters) will it rise?

Question

I tried using h=1/2gt^2

and then Vf = Vi-gt
and h = Vit - 1/2gt^2 and ended up with a final answer of 10.53.
Its wrong, so i'd like to know how to properly do this problem.