1) you have to find the difference between pipe A and pipe B, which is 6.40.
23.55-17.15=6.40
2) after finding the difference. You will take that difference and put it out of 23.55 and multiply by 100 to get your percentage. As so:
(6.40/23.55)(100)= 27.176% which rounds to 27% as a whole number.
Your answer is 27%. Hope that helps!