I assume you mean the total number of jazz and classical songs combined is 28 songs? 3 times as many jazz as classical: Means there is a ratio of 3 jazz to 1 classical, which means there are essentially 4 parts (3+1=4). So if we divide 28/4=7. This gives one part = number of classical songs, jazz is 3 parts so 7*3=21 jazz songs. 7 times as many rock as classical: From above we know there are 7 classical songs. 7*7=49 rock songs. Jazz=21 songs Rock=49 songs