Correct option is A
In this series following pattern is followed-

Logic: in the first row +6 is added. so next term in first row = 24 + 6 = 30
In the second row is subtracted by 6, 12, 18 , so next term in second row = 42 - 24 = 18.
finally the numbers in each term in each row changes the place alternatively.
Correct answer is (a).







