Hey there! 
Since we don't have values for b, d, and r, we can't get a specific number for the value of a, if that makes sense. It'll be represented by these variables. 
To solve, we need to make sure the equation looks like a = ? . 
Subtract b from each side of the equation. 
<u>a = dr - b </u>
Now we have solved for a. 
Hope this helps!
 
        
             
        
        
        
Answer:
X is just the variable or missing edge, side, angle .etc that you are looking for
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
72.2
Step-by-step explanation:
Monday: 78.8
Tuesday: 78.8 - 6.6 = 72.2
 
        
             
        
        
        
Answer:
A
Step-by-step explanation:It Said on Usa Test prep