We know that the height of the flagpole is 5.5 plus the height that is left, so we will call the height x + 5.5.
Now we now that the angle of elevation is 23 and the side of the bottom of "the triangle" is 30. So we can conclude that tan 23=(x/30)
x= 30tan23
The height would be 30tan23 + 5.5 which is 18.23 ft.