You already have the unit price of brand B which is 17x. Now you need to find the unit price of brand A. Since you can see that you need to multiple 11 by each bottle (x), the unit price is 11x.
The question asks for the price of 8 bottles, so plug 8 for each x:
Brand B: (17)(8)= 136
Brand A: (11)(8) = 88
Now find the difference:
136 - 88 = 48
Your answer is $48.
Hope this helped!