B. 33.5 is your answer
First you want to add 12+4 because it is in parentheses 
8.5+16x2-7
Then you multiply 16 by 2
8.5+32-7
Then you add 8.5 to 32
40.5-7
Then you subtract 7 from 40.5 giving you your answer
33.5
        
                    
             
        
        
        
Answer:
6!
Step-by-step explanation:
chord x chord = chord x chord
(5) (n+8) = (7) (n+4)
i just started plugging in numbers 
(5) (6+8) = (7) (6+4)
5 x 14 = 7 x 10
70=70