The ticket prices for a concert series were $12, $37, $45, $18, $8, $25, and $18. what was the ticket price of the eighth and final concert in this series if the set of 8 prices had a mean of $23, a mode of $18, and a median of $19.50?

Given:
12, 37, 45, 18, 8, 25, 18, ?
mean = 23
mode = 18
median = 19.50

using the mean
23 * 8 = 184
12 + 37 + 45 + 18 + 8 + 25 + 18 = 163
184 - 163 = 21

data set arranged in order from least to greatest:
8, 12, 18, 18, 21, 25, 37, 45

using the median
18 + 21 = 39
39 / 2 = 19.50

The missing ticket price is 21.