using the given equation, d would be the distance which is given as 7 miles.
replace d with 7 and solve for h
7 = 5/6 SQRT(h)
divide both sides by 5/6
7 / 5/6 = sqrt(h)
8.4 = sqrt(h)
raise both sides to the 2nd power:
8.4^2 = h
h = 70.56
h = 71
The answer is B. 71 feet.
