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 150 and 350 is 200.

Next, we need to find what percentage of the original number the absolute difference represents. To do this, we divide the absolute difference by the average of the two numbers (which is (150+350)/2 = 250).

So, the percentage difference between 150 and 350 is:

(200/250) x 100% = 80%

Therefore, the percentage difference between 150 and 350 is 80%. This means that the difference between 150 and 350 is 80% of the average of the two numbers.