Question

7 15 8 5 12 2 2 ? 3 109 183 168

Answer 1

answer is 9

The above Series is segregated into three different rows.  

7 5 2 109  

15 12 x 183

8 2 3 168

From first row it is concluded that

(cube of 1st  number -cube of 2nd number )/3rd number=4th number  

i.e. (73-53)/2

=(343-125)/2

=109

Therefore, (153-123)/x=183

(3375-1728)/183=x

1647/183=x

X=9

Answer is 9  

see in attachment