The correct answer is right.
An acute one would have all three acute, while an obtuse one would have at least one obtuse angle. 
        
                    
             
        
        
        
Domain is the values of x. x is from -5 to 7, it includes -5 ([ ] is the include symbol, but doesn't include 7, so C is the answer
        
                    
             
        
        
        
-6+3-3(-18)
Okay. 
Work from left to right. 
-6 plus 3 equals -3. 
(Think of it as in a number line, from the spot of -6, move right three units. This will give you -3. Anyways..)
Now you have -3-3
The result is -6.
-6(-18)
Negative six times negative eighteen equals positive 108.
The answer is 108. 
(Sorry for the long reply)