From the top of a house 80m high, the angles of elevation

Question

and depression of the top and bottom of a hill are 60º and
30º respectively. Find the height of the hill

Answer 1

If the distance from the house to the hill is x, then
80/x = tan30°
x = 80√3
The height of the hill is thus
h = 80 + 80√3 tan60° = 320 m

Or, note that you have two similar 30-60-90° right triangles.
If the line-of-sight distance from the top of the house to the bottom of the hill is x, then
x/80 = 2
h/x = 2, so h = 2x = 320 m