Answer:
y = 3x -18 ( where y =  balls sent back by Rudolf; x= balls  given to Rudolf)
Step-by-step explanation:
x (Balls given)       y( Balls sent back)
8                             6                    Δy/Δx  = (27-6)/(15-8) =  3
15                            27
25                           57                 Δy/Δx  = (57-27)/(25-15) =  3
Observing the number sequence shows constant gradient and as such we can use equation of a straight line to relate the two variables.
Using the equation of a straight line we have:
(y-y1)/(x-x1) =  (y2-y1)/(x2-x1)
y-6/x-8  =       (27-6)/(15-8) 
y-6/x-8  =    3
y-6        =  3(x-8)
y-6  = 3x - 24
y = 3x-18
 
        
             
        
        
        
Answer:
5.89E+12
Step-by-step explanation: