Answer: Undefined
The x coordinates are the same, so a vertical line forms. All vertical lines have undefined slopes.
We can see it through the slope formula
m = (y2-y1)/(x2-x1)
m = (3-(-6))/(2-2)
m = (3+6)/(2-2)
m = 9/0
We cannot divide by zero, so the result is undefined. 
 
        
                    
             
        
        
        
Answer:
p = 8
Step-by-step explanation:
Subtract 18 from behind the equal sign to cancel it out. This leaves you with 2(p+1)- 18= 0.
Next you'll need to pull out the terms to work with the beginning of the problem. 2(p+1)- 18= 0 would turn into  2p - 16  = 2(p - 8).
This would leave you with 2= 0, but that's not true so continue on to the variable. 
So p - 8= 0 making the answer p = 8
 
        
             
        
        
        
Choose the 5th box, then the answer is 720in
        
             
        
        
        
So the equation looks like this : 15*3x=78
subtract 15 from both sides:        -15      -15
then divide by 3 from both sides
to isolate the variable:                  3x=63
                                                      3/3x=63/3
                                                        x=21 (your mystery number is 21)