Consider the equation y = 4.2x and the table below that represents this relationship. x= 0, 2, 4, 6, y= 0, 8.4, 16.8, 25.2

Please present the relationship in a table arranged vertically:

this relationship. X= 0, 2, 4, 6, Y= 0, 8.4, 16.8, 25.2   becomes:

 x        y
---   
 0       0
 2      8.4
 4     16.8
 6     25.2

Notice that as x increases by 2 units from 2 to 4, y increases by 8.4 units to 16.8.  Thus, the slope of this line is 
        16.8
m = = 8.4
          4-2

Your problem statement sounds incomplete; what were you asked to do here?

You could compare the equations of the 2 functions:

y = 4.2x and
y = 8.4x 

The slope of the 2nd function is twice that of the first function.  Both graphs go through the origin, (0,0).