Assignment: 
<><><><><>
Answer: 
<><><><><>
Explanation: 
<><><><><>
Note: 
[ Step One ] Apply Rule - (-a) = a

[ Step Two ] Add

<><><><><><><>
Your answer would be -11.
Answer:
(x-8)/10
Step-by-step explanation:
-------
I think you can use cosine rule if only the lines that form the <52 are equal.
I hope this helps you
90-8.5
90-40
50