Answer: a-b+c+d =4
Step-by-step explanation:
The given system of equation is 

from this we have the following matrices

 the given matrix A =
On comparing Matrix   with Matrix A
 with Matrix A

we have the following values
a=2 ,b=4,c=8,d=-2 
Thus a-b+c+d =2-4+8+(-2)=4
 
        
                    
             
        
        
        
They both equal so symbol is "=" they have LCM of 3 . 
 
        
                    
             
        
        
        
22b+17s ≤ 80
Where b is cost of belt,s is cost of shirt .
U can put some values foe b and c their sum always less and maximum would be 80