Hi. Let's start by using some letters to signify each person.
K = Kelly
L = Lou
T = Tiffany
Now, the total of all the songs these three individuals have on their digital devices is 682. So K + L + T = 682.
We know that Kelly has four times as many songs as Lou, so K = 4L. We also know that Tiffany has six times as many songs as Lou, so T = 6L. We can substitute those values for K and T in our equation. So it becomes this:
4L + L + 6L = 682
11L = 682
682/11 = L
L = 62
So Lou has 62 songs on his device. If Kelly has four times the number of songs that Lou has, then she has 4 x 62 = 248 songs. If Tiffany has six times the number of songs that Lou has, then she has 6 x 62 = 372 songs.
Let's add those numbers up to see if they total 682. If they do, then we know we are right!
62 + 248 + 372 = 682. We are correct!!