#### Answer

18

#### Work Step by Step

2,7,12,5,10,15,8,13
the above pattern is as follows:
First numbers is obtained by adding 5 to the previous number(2,7,12)
Subtract 7 from the third number to get the fourth number of the series (12-7) =5
again add 5 to the set of next 3 numbers(5,10,15)
Again subtract 7 from the last number(15 -7) = 8
Again add 5 to get the next 3 numbers (8,13,18)
so the next number is 18