Fares on the city-run public buses in Greenville are subsidized by city tax revenues, but among the beneficiaries of the low fares are many people who commute from outside the city to jobs in Greenville.
Conclusion (therefore)
Bus fares should be raised enough to cover the cost of the service.
Evidence
Fares on the city-run public buses in Greenville are subsidized by city tax revenues.
Among the beneficiaries of the low fares are many people who commute from outside the city to jobs in Greenville.
Some city councillors argue that city taxes should be used primarily to benefit the people who pay them.
Evaluate
GIVEN THAT tax money helps pay for the bus, tax money is meant to benefit the people who pay those taxes, and this bus benefits some people who commute from outside Greenville,
HOW CAN WE ARGUE bus fares should not be raised?
Debating whether we "should" do something is all about comparing upsides to downsides.
The author thinks that raising the fare will get rid of the downside of "city taxes benefiting commuters". But maybe it would create new downsides (maybe the new fare would be too expensive for locals to continue using the bus).
Goal
Let's find four answers that defend the status quo or give us a way to say that raising fares would be a bad move, overall.