someone help I don't know this trig question

Answer:
Bill is 9.80 km apart from Concert
Step-by-step explanation:
It's given in the question,
m∠B = 75°
m∠C = 45°
By triangle sum theorem,
m∠A + m∠B + m∠C = 180°
m∠A + 75° + 45° = 180°
m∠A = 180° - 120°
m∠A = 60°
By sine rule,
[tex]\frac{\text{sin}(\angle A)}{BC}=\frac{\text{sin}(\angle C)}{AB}[/tex]
[tex]\frac{\text{sin}(60)}{BC}=\frac{\text{sin}(45)}{8}[/tex]
BC = [tex]\frac{8\text{sin}(60)}{\text{sin}(45)}[/tex]
= 9.80 km
Therefore, Bill is 9.80 km apart from Concert.