At an office supply store pens were marked down from 150 to 120 what percent discount is that

The pens were 20% off of the original price

You would use the equation:

"difference divided by original price"

So the difference between 150 and 120 is 30 and the original price is 150.

Then you would do 30 divided by 150 which would give you 0.2.

And In a percentage it would be 20%. So it is a 20% discount.