Really, it is not all that difficult.
You do not need number values.
In fact when a system is first being analyzed or designed nobody has any numbers. It is best to first find out what is important, and that is what this problem is about.
stone 1 ( or a , or zamba or whatever you want to call it )
Initial velocity v1
initial height h1
initial time t1
acceleration a = g ( gravity )
Now using these values, and an equation of rectiliner motion, you can find stone1 position.
Stone 2
Initial velocity v2
initial height h2
initial time t2
acceleration a = g ( gravity )
Now using these values, and an equation of rectiliner motion, you can find stone2 position.
Then, I leave it up to you to figure out what the question asks "While they are still in flight ,find the functional form of the vertical distance between them as a function of time".