Please answer a question about the following article about Charleston, South Carolina:

The City of Charleston is served by the Charleston International Airport. It is located in the City of North Charleston and is about 12 miles (20 km) northwest of downtown Charleston. It is the busiest passenger airport in South Carolina (IATA: CHS, ICAO: KCHS). The airport shares runways with the adjacent Charleston Air Force Base. Charleston Executive Airport is a smaller airport located in the John's Island section of the city of Charleston and is used by noncommercial aircraft. Both airports are owned and operated by the Charleston County Aviation Authority.

How far is the airport from downtown Charleston?
12 miles (20 km)