Question 1182020
Draw this triangle with AB=8 an AC=9.
Angle A is 60 degrees, because the angle from AB to the South line is 40 degrees and there is 20 more degrees to reach AC.
Use the law of cosines.  
side a^2 opposite to angle A=b^2+c^2-2bc CosA
=64+81-2(72)*0.5
=145-72
=73 km^2
a=8.544 km, and this is the distance between B and C.