Let x= number of songs on Lou’s player
Let k= number of songs on Kelly’s player
Let t= number of songs on Tiffany’s player
x+k+t=682
k=4x
t=6x
Now use substitution
x+(4x)+(6x)=682
11x=682
Divide both sides by 11 and get x=62
To find how many songs Kelly has, substitute 62 for x in k=4x to get k=248
Kelly has 248 songs on her music player