Verbal Reasoning - Mental Ability Questions

The given sequence is a combination of two series
1)31,35,39,43,47
2) 45,47,49,51,53
So,the missing term is 49

We know that a negative value plus a positive value always count backward and the sign depends on the bigger value sign.

When you are adding a negative number to a positive number, then the value counts backward and takes the sign of the biggest number.

For example::

Adding -5 and +2

-5 + 2 = -3 (big number is 5 and its sign is '-')

Adding -3 and  +5

+5 + (-3) = 5 - 3 = +2(big number is 5 and it has sign '+').  

My only son's sister is my daughter
father of my daughter is me only
her brother means she is my 'sister'.

The sequence consists of two series (Y, T, O) and (B, G, ?). The first series consists of 2nd, 7th and 12th letters from the end of English alphabet. The second series consists of 2nd, 7th and 12th letters from the beginning of English alphabet.