To find the percentage difference between two numbers, we first need to find the absolute difference between them. In this case, the absolute difference between 137 and 116 is 21 (137 - 116 = 21).

Next, we need to find the average of the two numbers. The average of 137 and 116 is (137 + 116) / 2 = 126.5.

Now, we can calculate the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 137 and 116 is (21 / 126.5) x 100 = 16.63%.

Therefore, the percentage difference between 137 and 116 is 16.63%. This means that the two numbers differ by 16.63% of their average value.