Phillip earned \( \$ 12, \$ 25, \$ 15 \), \( \$ 18 \), and \( \$ 20 \) for each of five dogs he walked. Phillip wants to earn a mean of \( \$ 20 \) per dog. How much must he charge the next time he walks a dog?

To find out how much Phillip needs to charge for the next dog to achieve a mean of $20 per dog, first calculate his total earnings from the first five dogs: \[ 12 + 25 + 15 + 18 + 20 = 90. \] He walked 5 dogs, so to find the total amount he needs to earn for 6 dogs to achieve an average of $20: \[ 20 \times 6 = 120. \] Now, subtract the total he has already earned: \[ 120 - 90 = 30. \] So, Phillip must charge **$30** the next time he walks a dog to reach his goal of a mean of $20 per dog.