Hi there!
Your question:
Sales fall from 300 per week to 270 per week what's the percentage change?
My answer:
The formula for calculating percent change is as follows:
[(y2 - y1)/y1]*100=your percent change
y2= first value
y1=second value
Plug the numbers in:
[(300-270)/300]*100
[30/300]*100
0.1*100
10
Therefore, the percent change is 10%
Hope this helps! Let me know if it's incorrect so I can fix it:)