Answer:
A real world problem would be the rate of inflationary index across a month, where x is the day and y is the inflationary index by day in a given country.
If the country has a good economy, the inflationary index is almost constant or decreasing as best, a line could represented it
If the country has not a good economy, the inflationary index is escalating , in special circumstances the behavior is not linear, is something else.
