Answer:
The distance between Mercer and Turtle Lake is 25.57 km
Explanation:
Law of cosines
When a triangle is defined by two of its sides and the angle formed by them, we can apply the law of cosines to know the third side. Being a and b the known sides and
the angle, we write the law of cosines as

In our case:




The distance between Mercer and Turtle Lake is 25.57 km