The question GIVES us an equation:
V₀ = √(v² - 64h) .
It TELLS us that v should be 100 ft/sec and h is 150 ft.
All we have to do is plug the numbers into the equation,
and then do the arithmetic to find V₀.
There's not even any Physics to do. Only arithmetic.
V₀ = √(v² - 64h)
v = 100
h = 150
V₀ = √(100² - 64·150)
V₀ = √(10,000 - 9,600)
V₀ = √400
V₀ = 20 ft per sec .