Answer:
Option b - Subtract
Step-by-step explanation:
Given : Expression 
To find : Which operation should be completed first in the expression below?
Solution : 
P - Parentheses
E - Exponent
D - Divide 
M - Multiplication 
A - Addition 
S - Subtraction
In the first step we solve the bracket in the expression  
So, we do subtraction i.e. 12-8=4
Therefore, option b is correct.
 
        
             
        
        
        
C is correct because A is 2.82 and B is 2.8
        
                    
             
        
        
        
The second graph I believe if not some else will try to help.