Selling price of app per user = $10 per month
Total no. of user in first month = 10
To tal no. of user added per month = 7
We have to find how much money is earned in one year 
So the formula is n/2 * (2a +(n-1)d)
Here we have n = 12 which is total no. of months
a = 100 , which is money earned in one month 
d = 70 , which is increase in money earned per month
So money earned in a year comes out to be 5820
 
        
             
        
        
        
That makes no sense I think you’re missing some words but the answer might be $7.5 per hour bc 21-6 is 15 and that divided by 2 s 7.5
 
        
                    
             
        
        
        
Answer:
uhh, look it up
Step-by-step explanation:
 
        
             
        
        
        
<span>Rock, Carbon, Water, Nitrogen</span>