Total number of guests = 278
So, x + y + z + 21 + 20 + 9 + 23 = 278
Or x + y + z = 205 --- (1)
As, there were equal numbers of bottles of each of the three kinds (Pepsi, Dew and Sprite), we have:
x + 21 + 9 + 20 = y + 21 + 9 + 23 = z + 20 + 23 + 9
Or, x + 50 = y + 53 = z + 52--- (2)
On solving Eq. (1) and (2), we get:
x = 70, y = 67 and z = 68
So, final Venn diagram is as below:

Number of guests who enjoyed Dew or Sprite but not Pepsi = 68 + 23 + 67 = 158
So, the correct answer is E.