Answer:
When I did this in middle school, the teacher made it unnecessarily difficult (-_-), so here`s my own method for you.
Finding 1%:
If 9 is 3%, then 3 is 1%. This method only works when the sides are divisible.
You can use the 1% to find the total, which is 100%.
3 stores (or 1%) x 100 = 300.
There are 300 stores in the shopping district.
Hope that helps
