Final answer:
To find the regular price of the haircut, divide $9 by 0.60.
Step-by-step explanation:
To find the regular price of the haircut, we need to determine 100% of the price. Since Charles paid $9, which is 60% of the regular price, we can set up the equation: 60% of x = $9. To solve for x, we divide $9 by 0.60:
x = $9 / 0.60 = $15
Therefore, the regular price of the haircut is $15. The correct answer is option c) $15.