y = kx, so y/x = k
You have two values of y and x from the table, (4,28). Hence:
k = y/x = 28/4 = 7
So the equation is y = 7x.
Now we can complete the table. For the entry x=2, we can compute y= 7x = 7*2 = 14, so put a 14 below the 2 in the table. You should be able to complete the rest of the table on your own now.