Is this what you’re looking for 
y=-2/5x+3/5
        
                    
             
        
        
        
That is a ratio. 7 x 3 = 21 and 13 x 3 = 39.
        
             
        
        
        
Your answer would be 1...
        
                    
             
        
        
        
Answer:
First term (a) =8
Common difference (d)= t2-t1
 =12-8
 =4
Now, sum of first 31th term (tn31) =n/2{2a+(n-1)d}
  = 31/2{2×8+(31-1)4}
 =31/2{16+(30×4)
 =31/2(16+120)
 =31/2×126
 =31×63
Step-by-step explanation:
Similarly use 19 as (n) for the 19th term 
 
 
        
             
        
        
        
Step-by-step explanation:
No. of points got from 1 stunt = 50.
No. of points deducted from 1 fail = 40.
6 stunts and 9 falls were gained last week.
So, A/C the number of points earned = 
(6×50)-(9×40)
= 300 - 360
= -60
Her score today is 3 times her score from last week so multiply by 3
= (-60) × 3
= -180
If it were multiplied by -3 instead of 3 it would be...
 (-60) × (-3)
= 180
The difference would be that on multiplying with positive 3 she would be 180 points in the whole but multiplying with negative three means she is 180 points in the league.
The similarity is that that whole number is same but the symbol adds a difference and the absolute value would be same too.