Explanation:
This problem is a good example of Vertical motion, where the main equation for this situation is:
[tex]y=y_{o}+V_{o}t-\frac{1}{2}gt^{2}[/tex] (1)
Where:
[tex]y[/tex] is the height of the stone at 6s (the value we want to find)
[tex]y_{o}=925ft[/tex] is the initial height of the stone
[tex]V_{o}=20ft/s[/tex] is the initial velocity of the stone
[tex]t=6s[/tex] is the time at which we need to find the height
[tex]g=32ft/s^{2}[/tex] is the acceleration due to gravity
Having this clear, let's find [tex]y[/tex] from (1):
[tex]y=925ft+(20ft/s)(6s)-\frac{1}{2}(32ft/s^{2})(6s)^{2}[/tex] (2)
Finally:
[tex]y=469ft[/tex] This is the height of the stone at t=6s