Hey there!
The answer to your question is 
Given:

First, we distribute the negative sign to both terms (
) This would make the
negative and the
positive, so we have:

Add them together and we get:

Have a nice day!
Answer:
I believe Jamal is correct, because he is just doing it an easy way. Instead of converting the mixed number to an improper fraction he is adding the measurements step by step.
Hope it Helps!
:)
∠B + ∠B` = 180°
The Sine Law:
10 / sin B` = 9.2 / sin 60°
10 / sin B` = 9.2 / √3/2
sin B` = 0.94133
B` = sin^(-1) 0.94133
Answer:
C ) ∠B` = 109.73°, ∠B = 70.27°