Here are two stories: The initial freshman class at a college is 10% smaller than last year’s class. But then during the first week of classes, 20 more students enroll. There are then 830 students in the freshman class.
A store reduces the price of a computer by $20. Then during a 10% off sale, a customer pays $830.

Here are two equations:
0.9x+20=830
0.9(x−20)=830

Which story is represented by 0.9x+20=830?