To understand the percentage difference between 9 and 12, we first need to understand what percentage difference means. Percentage difference is a way to measure the difference between two values as a percentage of one of the values. In this case, we are comparing 9 and 12.

To find the percentage difference between 9 and 12, we first need to find the absolute difference between the two values. The absolute difference is simply the difference between the two values without considering whether they are positive or negative. In this case, the absolute difference between 9 and 12 is 3.

Next, we need to find the average of the two values. The average is simply the sum of the two values divided by 2. In this case, the average of 9 and 12 is (9+12)/2 = 10.5.

Now, we can find the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 9 and 12 is:

|9-12| / 10.5 x 100 = 28.57%

Therefore, the percentage difference between 9 and 12 is 28.57%. This means that 12 is 28.57% greater than 9.