For this case we can use the following rule of three:
$ 500 ---------> 100%
$ 400 ---------> x
Clearing x we have:
x = (400/500) * (100) = 80%
Therefore, the percentage of decrease in the rent is:
p = 100-x
p = 100-80
p = 80%
Answer:
a proportion can be used to calculate p is:
p = 100 - ((400/500) * (100))
