If the money supply in an economy is $100,000, currency in circulation is $50,000, amount in savings accounts is $18,000, travelers' checks is $12,000, and the amount in money market accounts is $9,000,

then what is the amount held in checking accounts in the economy?

The total money supply in an economy is the sum of currency in circulation, amount in savings accounts, amount in checking accounts, travelers' checks, and the amount in money market accounts. Hence, the amount in checking accounts is $100,000 - $50,000 - $18,000 - $12,000 - $9,000 = $11,000.