To find the percentage difference between two numbers, we first need to calculate the absolute difference between them. In this case, the absolute difference between 17 and 25 is 8.

Next, we need to find the average of the two numbers. The average of 17 and 25 is (17+25)/2 = 21.

Now, we can calculate the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 17 and 25 is:

|17-25| / 21 x 100 = 8/21 x 100 = 38.1%

Therefore, the percentage difference between 17 and 25 is 38.1%. This means that 25 is 38.1% greater than 17.