Final answer:
Francesca must paint 11 faces in order to earn $80.
Step-by-step explanation:
To find the number of faces Francesca must paint to earn $80, we need to determine how many $5 face paintings she needs to exceed her initial purchase of $25 worth of supplies and reach $80. This can be done by setting up an equation:
25 + 5x = 80
where x represents the number of face paintings.
Now we can solve for x:
5x = 80 - 25
5x = 55
x = 55/5
x = 11
Therefore, Francesca must paint 11 faces in order to earn $80.