The statement is always true because right angles measure 90 degrees and if you add them you get 180 and supplementary angles are angles that add up to 180.
Hope this helps :)
        
             
        
        
        
All you need to do it combine like terms.
3x + 9 + 4x + x
(3x + 4x + x) + 9
8x + 9
i hope this was helpful for you!
        
             
        
        
        
Answer:
360
Step-by-step explanation: A full angle is 360. 90*4=360. 
 
        
             
        
        
        
There are quite a few websites that have factor lists. Also, if you can find the biggest number that goes into it, then all of the factors of that number go into it as well.