Final answer:
The zero of the function n=20-2.75c is found by setting n to zero and solving for c, which results in Enrique being able to buy 7 cups of coffee before his gift card runs out of funds.
Step-by-step explanation:
To find the zero of the function n=20-2.75c, which represents the amount of money Enrique has on his gift card after purchasing c cups of coffee, we need to set n to zero and solve for c:
0 = 20 - 2.75c
2.75c = 20
c = 20 / 2.75
c ≈ 7.27
Since Enrique cannot buy a fraction of a cup of coffee, he can buy 7 cups of coffee before the card's balance reaches zero. The zero of the function indicates that the gift card no longer has any funds remaining after purchasing 7 cups of coffee at $2.75 each.