Answer:
The equation is;
d = 1.25s
Explanation:
Here, we start by getting the price of a single song
From the question;
4 songs = $5
Thus, 1 song will be $5/4 = $1.25
So the proportionality constant is $1.25 per song
To write the relationship, we have;
d = 1.25s
Where d is the cost in dollars and s is the number of songs