The rainfall, r, is inversely proportional to the water shortage, s, in a city. if the rainfall in the city is 40 inches, there is a water shortage of 200 million gallons per day. which statement best describes the inverse relation of the rainfall in terms of the water shortage?

This is the concept of proportionality, to model the above information we proceed as follows;
given r is inversely proportional to water shortage, then:
r α 1/s
hence;
r=k/s
where;
k is constant of proportionality;
k=rs
thus when r=40 inches and s=200 million then:
k=(40*200) million
=8000 million
hence the formula for rainfall will be;
r=(8000 million)/s