Hello, Sohail!

Did you make a sketch?

A point is 12 km due north of another point .

The bearing of a lighthouse from is 135°, and from it is 120°.

Calculate the distance .Code:| P * 135° | * |45°* r=12 | * | * | * Q * 120° * * * q * * * * * * * * * * * * *15°* * * * R

In , we have: . , then

. . also: .side and we want side

Law of Sines: .

Therefore, we have: . km.