Step-by-step explanation:
Given 
2a + b = 6......equation 1
a - 6 = b
a = b + 6........equation 2
Putting equation 2 in equation 1 
2 ( b + 6 ) + b = 6
2b + 12 + b = 6
3b = 6 - 12
3b = - 6
b = - 6 / 3
Therefore  b = - 2
Now 
a = - 2 + 6 = 4
hope it will help :)
 
        
                    
             
        
        
        
Answer:
10 in
Step-by-step explanation:
 
        
             
        
        
        
I’d say 10 or 11 but I’m not 100%