Hello!
First, we know K = ΔUg. (From now on, I'm going to use a lowercase g as your subscript g). We therefore can say that 1/2mv^2 = mgh, as K = 1/2mv^2, ΔUg = mgh, and K and ΔUg are equal.
From this equation, substitute in values and divide both sides by m.
1/2mv^2 = mgh
1/2mv^2 = m(9.8)(10)
(1/2mv^2) / m = (m(9.8)(10)) / m
1/2v^2 = (9.8)(10)
Now, we have an easily solvable equation.
1/2v^2 = (9.8)(10)
1/2v^2 = 98
v^2 = 196
v = 14
Therefore, your answer is v = 14.
Hope this helps!