This problem is ill stated.
Unless you've left some info out there are infnite solutions for y in terms of x.
There end up being two free parameters, v0 and theta, the angle at which the throw is made with
respect to the x axis.
The ball could the thrown straight up and satisfy what's given or it could thrown at any angle and
a v0 could be found to solve the conditions listed.
Did you leave something out?