basically it is telling us
vertical distance is y(t)=-16t²+425t+8200
horizontal distance is x(t)=113t
so if it lands at a certain vertical distance, it travaeld a certain distance, t. so if you are given a distance it ended at, we can solve for a time
so we have that it landed at ELEVATION of 6000 ft
y(t)=6000
solve for t
because
-16t²+425t+8200=y(t) so it equals 6000 so solve for t
-16t²+425t+8200=6000
times -1 both sides
16t²-450t-8200=-6000
add 6000 bot obht isdes
16t²-450t-2200=0
factor using math
use quadratic formula
t≈-4.44 or t≈30.99
can't be negative time so t≈30.99
so find the horizontal distance
x(t)=113t
x(30.99)=113(30.99)
x(30.99)=3502.8
rounded
3500
answer is C