Answer:−x2−6xy+8y2+9yz−12
 
 
        
             
        
        
        
Answer:
x=8,10if this helps then your welcome if not I apologize 
 
        
             
        
        
        
Answer:
x=5 and y=-2
Step-by-step explanation:
3x+5y=5
-(7x+5y=25)
-4x=-20
x=5
plug 5 into one of the equations. 3(5)+5y=5
y= -2
 
        
             
        
        
        
Answer:
-82
Step-by-step explanation:
-18 - 64
-82
Answer:  -82
 
        
             
        
        
        
I think it would be 10.5, although I'm not sure I hope this helps