From a point on level ground 15 m from the foot of a tower, the angle of elevation of its top is…

Height from a ground distance: $h = d \tan \theta$. Height from a slanting length: $h = \text{length} \times \sin \theta$. If the eye is above the ground, add the eye height at the end. $\tan 30° = \dfrac{1}{\sqrt{3}}$, $\tan 45° = 1$, $\tan 60° = \sqrt{3}$.