You will need to paint 9 faces in order to earn $15. I solved this problem by setting up an equation using the given information. The equation is 15=3x - 12. 15 is the goal amount of profits. 3x represents $3 per person/face charge. I subtracted $12 from that because it is the money used to buy paint supplies. After that, i solved for x. The answer is 9 faces. Hope this helped you! I included a picture of my work :))
