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 80 and 75 is 5.

Next, we need to find the average of the two numbers. The average of 80 and 75 is (80+75)/2 = 77.5.

Now, we can find the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 80 and 75 is (5/77.5) x 100 = 6.45%.

Therefore, the percentage difference between 80 and 75 is 6.45%. This means that 75 is 6.45% less than 80.