You start with f(x)=8-3(3)². Then, going in order of PEMDAS, you start with your exponent. So you have f(x)=8-3(9). Then multiplication, f(x)=8-27. Then your subtraction. f(x)=-19
given h = 600 - 16t ( add 16t to both sides )
16t + h = 600 ( subtract h from both sides )
16t = 600 - h ( divide both sides by 16 )
t = 
when h = 400
t =
=
= 12.5 seconds