If the price of a good in the U.S. is $10, the exchange rate is 2 units of foreign currency per dollar, and the foreign price of the same good is 30 units of foreign currency, then the real exchange rate is 2/3.

Real Exchange Rate

The relative price of the goods and services of one country compared to those of another when expressed in a common currency.

Foreign Currency

Money or other forms of financial assets denominated in the currency of a country that is not the domestic country of the holder.