WASHINGTON — The U.S. Supreme Court next week hears a challenge to President Barack Obama’s health-care overhaul that hinges on just four words in the massive law that seeks to dramatically reduce the ranks of the uninsured. The argument threatens subsidies that help make insurance affordable to consumers in about three dozen states. The lawsuit focuses on the health insurance marketplaces, or exchanges, that have been set up to allow people to find coverage if they don’t get insurance through their …