I'll treat these like they're two seperate problems because  how you set it up they're not together. If it's one whole problem please tell me and I'll solve it that way. :-)
First one: 3x+9+8x + 12
Collect like terms and simplify
(3x+8x)+(9+12)
11x+21
Second one: 2x + 6+x² + 6x + 9
Collect like terms and simplify

8x+15+
Hope this helps you, have a BLESSED and wonderful day, as well as a safe one!
-Cutiepatutie ☺❀❤
 
        
             
        
        
        
Answer:
the correct answer would be A. the mean is when you add up all of them and divide it by how many numbers there are which in this case is 5. and the median is the number in the middle, in this case 20, therefore when you add up all numbers in A ,you get 105 and you divide it by 5 which gives you 21. :))
 
        
             
        
        
        
Answer: If the question is formed as (- 3/5) x = 15
then A is correct
X=-25 
 
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:±17.6635217326557
Step-by-step explanation:
 
        
             
        
        
        
ABCD is a square and a quadrilateral