The sum of 4 consecutive odd numbers is 40. what is the 2nd number in this sequence?

Try this option (it is not the only way):
1. if to use for consecutive odd numbers: n; n+2; n+4 and n+6), then it is possible to write their sum in equation: n+n+2+n+4+n+6=40.
2. if to solve this equation: n=7 it means that 7 - the 1st number of the given sequence.
Using n=7 the 2d number of this sequence is n+2=9.

9.