Answer:
3rd Matrix
Step-by-step explanation:
When you start putting the coefficients in as the matrix, you see that -9 has to be the 1st number, so that eliminates choice B and choice D as answers. You are left with choices A and C. C is the correct choice because when you plug in the second equation, your coefficient is -5, not 0.
 
        
             
        
        
        
The answer is B. The leading coefficient is always the variable with the highest degree. In this case, it's 5.
        
                    
             
        
        
        
Answer:
2n - 4.
Step-by-step explanation:
(n+8) + (n−12)
= n + 8 + n - 12
= n + n + 8 - 12
= 2n - 4.