Question

Can someone help me with this

Answer 1

Answer: 8.2

Step-by-step explanation:

As angles in a triangle add to 180 degrees,

$\angle A=180^{\circ}-121^{\circ}-31^{\circ}=28^{\circ}$

So, by the Law of Sines,

$\frac{a}{\sin A}=\frac{b}{\sin B}\\\\a=\frac{b \sin A}{\sin B}\\\\a=\frac{9 \sin 28^{\circ}}{\sin 31^{\circ}}\\\\a \approx \boxed{8.2}$