Answer:
9
Step-by-step explanation:
See attached photo for solution
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Since jason is currently at 54 feet above sea level and David is 11 feet below sea level the add 11 plus 54 which would give you 65 feet is there distance of elevations
hi
-16t²+250 = 75
-16t² = 75 -250
-16t² = -175
t² = -175 /-16
t² = 175/16
Here there si two solutions : t =
and t = - 
However, as time cannot rewind, we will keep only positive solution
So t = 
in seconds it will be : 3.3 seconds