3. si tuvieras que escoger un movimiento para estudiarlo, ¿cuál sería? ¿por qué?

2nd Option is correct.

Step-by-step explanation:

Given:

Renata has $20 in gift card.

She bought 16 songs.

After purchase Balance in gift card = $0

⇒ Cost of 16 songs = $20

⇒ Cost of 1 song = 20/16 = $ 1.25

let x represent number of songs purchased and y represent balance on her gift card.

So, Cost of x songs = 1.25 × x = 1.25x

And Balance = 20 - 1.25 x

Thus, Required equation representing relationship between balance on gift card and number of song purchased.

y = 20 - 1.25x

1.25x + y = 20

If we multiply both sides of equation with 4, we get

5x + 4y = 80

Therefore, 2nd Option is correct.