Two buildings are in front of each other on a road of width 15 meters.

Let’s assume the position of the observer on the lighthouse as point A, and the position of the ship on the ground as point B. Also, let’s assume the height of the ship above the ground level as h, and the horizontal distance between the light-house and the ship as x.

Now, from the given information, we know that:

• The height of the light-house, AC = 100 meters
• The angle of depression from the observer to the ship, CAB = 30°

We need to find the distance between the light-house and the ship, AB = x.

To solve for x, we can use trigonometry. Let’s consider right-angled triangle ABC:

• AB is the hypotenuse
• AC is the opposite side of angle CAB
• BC is the adjacent side of angle CAB

Using the trigonometric ratio for tangent, we get:

tan CAB = AC/AB tan 30° = 100/x 1/√3 = 100/x

Solving for x, we get:

x = 100√3 ≈ 173.2 meters

Therefore, the ship is approximately 173.2 meters away from the light-house.