For example, y=x+4 and y=5x+2.
That would mean that x+4=y=5x+2.
Simplify it to x+4=5x+2.
x=5x-2
-4x=-2
x=1/2.
Now, plug x into one of the equations.
y=x+4
y=1/2+4
y=9/2.
Therefore, the POI is (1/2,9/2).
        
             
        
        
        
Answer:
483 840 ways
Step-by-step explanation:
Let you and your friend be A and B.
With three people always between you two,, we have 
Case 1: AxxxBxxxxx
Case 2: xAxxxBxxxx
Case 3: xxAxxxBxxx
Case 4: xxxAxxxBxx
Case 5: xxxxAxxxBx
Case 6: xxxxxAxxxB
So there is 6 ways of arranging you two through the line and for each of the six cases,
If you two remained in your positions, the rest can be arranged in 8! ways
Also for each case, you two can interchange your positions in 2! ways
Therefore,
The photographer can rearranged the line keep three people between you an your friend in 
8! * 2! * 6 = 483 840 ways
 
        
             
        
        
        
Imagine the area is 360 degrees, or 

 radians.
You would multiply it by (3/8) to get your answer.
 
        
        
        
Exception if the integer is a negative
        
                    
             
        
        
        
an equation in slope intercept form is 
y=mx+b