Answer:
midpoint is at (6.5, 6) im pretty sure, im sorry if im wrong 
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
40-15-12= 13
Step-by-step explanation:
15 + 12 + x = 40
Solve for x
 
        
             
        
        
        
Answer:
an = 2.5n -0.2
Step-by-step explanation:
an = 2.5n -0.2
 
        
             
        
        
        
Answer:
The sum of the first 650 terms of the given arithmetic sequence is 2,322,775
Step-by-step explanation:
The first term here is 4
while the nth term would be ai = a(i-1) + 11
Kindly note that i and 1 are subscript of a
Mathematically, the sum of n terms of an arithmetic sequence can be calculated using the formula 
Sn = n/2[2a + (n-1)d)
Here, our n is 650, a is 4, d is the difference between two successive terms which is 11.
Plugging these values, we have 
Sn = (650/2) (2(4) + (650-1)11)
Sn = 325(8 + 7,139)
Sn = 325(7,147)
Sn = 2,322,775