The maximum distance d in kilometers that you can see from a height h in meters is given by the formula d equals 3.5 times the square root of h. how high above ground must you be to see 35 kilometers?

First put the words in an algebraic format or a model. D = 3.5(√H). Now determine what the question is asking. It's height. Plug in the value of D. Distance is 35 km.
35 = 3.5(√H) We want to get H by itself. First thing to get away from it is 3.5. So                      divide 35 by 3.5 And 3.5(√h) by 3.5.
10 = √H        To get rid of √ do the opposite raise to the power of 2
10² = (√H)²   
100 = H 
You must be 100 kilometers above ground to see 35 kilometers