Answer:
given
n=9
a=1
d=3-1=2
Step-by-step explanation:
now , by formula, 
sn = n/2(2a+(n-1)d)
= 9/2(2×1+(9-1)×2)
=9/2×18
=81
 
        
             
        
        
        
Answer:
?????????????????????????
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
?=7
Step-by-step explanation:
Here is a cool trick that I believe only works with 9.
Add the numbers, 3+9+9+8+x= divisible by 9.
3+9+9+7+8 is 36 which is the only number divisible by 9.
 
        
             
        
        
        
Answer:
huh what do you mean 
Step-by-step explanation: 
im really sorry
 
        
             
        
        
        
Answer:
the answer is 1 because kyut ko hahaha