The time it took car P to travel 600 miles was 2 hours less than the time it took car R to travel the same distance. If car P's average speed was 10 miles per hour greater than that of car R, what was car R's average speed, in miles per hour?
SELECT DISTINCT Sno FROM SC S1 WHERE NOT EXISTS ( SELECT cno FROM SC S2 WHERE S2.Sno = '201215122 ' AND cno not in (SELECT cno FROM SC S3 WHERE S3.Sno=S1.Sno AND S3.Cno=S2.Cno) )
D.
SELECT DISTINCT Sno FROM SC S1 WHERE NOT EXISTS ( SELECT cno FROM SC S2 WHERE S2.Sno = ' 201215122 ' AND not EXISTS (SELECT * FROM SC S3 WHERE S3.Sno=S1.Sno AND S3.Cno=S2.Cno) );