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 173 and 200 is 27.

Next, we need to find the average of the two numbers. The average of 173 and 200 is (173+200)/2 = 186.5.

Now, we can calculate the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 173 and 200 is (27/186.5) x 100 = 14.48%.

Therefore, the percentage difference between 173 and 200 is 14.48%. This means that the second number (200) is 14.48% greater than the first number (173).