Ranata wins a 20 gift card to an online music site. Ranata purchased 16 songs and the gift card has a remaining balance of0. Which equation represents the relationship between y, the remaining balance of Ranata's gift card, and x, the number of songs purchased?
1) y = 20 - 16x
2) y = 16 - 20x
3) y = 20x - 16
4) y = 16x - 20
