according to the quesiton;
3x + 12 = 5x -4
12 + 4 = 5x - 3x
16 = 2x
16 / 2 = x
8 = x
x = 8
Now, substituting the value of "x" in one of the equation, we get,
3x + 12
= 3 (8) + 12
= 24 + 12
= 36
5x- 4 = 36 ...........because according to the question, 3x + 12 = 5x - 4
So, each of them have 36 songs