The formula gives the approximate distance to the horizon, d (in miles) given the height from the ground of a person's eye, h (in feet). Find the height of a person's eye if the horizon appears to be 8.8 miles away. (Only enter a numerical answer in the box below! No labels!) Round your answer to the nearest hundredth of a foot.

Unfortunately you did not state which formula you were given for

this problem, however ......

The common equation is
s = appr 3.6 √h , where s is in kilometres, and h in metres.
I see you are using the medieval units of measurement, so it would be

s = appr 1.2√h , where s is in miles and h is in feet
you are given that s = 8.8

so 8.8 = 1.2√h
7.3333...= √h
square both sides and you got it