11.Count of Countries by currency

 SELECT DISTINCT  CurrencyCode, Currency, NumberOfCountries
 FROM (
 SELECT   cur.CurrencyCode, cur.Description AS Currency, COUNT(c.CountryName) AS
 NumberOfCountries
 FROM Currencies cur INNER JOIN Countries c
 ON cur.CurrencyCode= c.CurrencyCode
 GROUP BY cur.CurrencyCode, cur.Description
 ) AS COUNTC

 ORDER BY NumberOfCountries DESC, Currency ASC