Let, the height of the tower, AB = h metre.

When the sun's angle of elevation was 45°, then the length of shadow of the tower is BD = x (let).

When the sun changes from 45° to 30°, then the length of shadow of the tower increases CD = 60 m (given)
And, when the sun's angle of elevation is 30°, then the length of shadow of the tower is BC = CD + BD = (60 + x) metre.
In ΔABD,