Final answer:
The next number in the series is 63.
Step-by-step explanation:
The series of numbers 3, 6, 9, 15, 24, 39 forms a pattern in which each number is obtained by adding the previous two numbers in the series. Let's break it down:
3 + 6 = 9
6 + 9 = 15
9 + 15 = 24
15 + 24 = 39
By following this pattern, the next number in the series can be obtained by adding 24 and 39:
24 + 39 = 63
Therefore, the next number in the series is 63.