Answer
The difference is approximately 2.398.
Work Step by Step
1. As mentioned in the question, the [H+] in A is 250 greater than in B.
$[H^+]^A = [H^+]^B \times 250$
2. Find the difference between the pH of solutions A and B.
$pH^B - pH^A$
$-log[H^+]^B - (-log[H^+]^A)$
*** Substitute the concentration of H+ in A, by the concentration of H+ in B multiplied by 250.
$-log[H^+]^B - (-(log[H^+]^B \times 250))$
$-log[H^+]^B - (-(log[H^+]^B + log(250)))$
$-log[H^+]^B + log[H^+]^B + log(250)$
$log(250) \approx 2.398$
