In a certain series, each number except the first and second is obtained by adding the previous two numbers. If the first no is 2 and sixth no is 26, then the seventh number is:

Answer: Option D

1^st no. = 2
2^nd no. = x (let)
3^rd no. = x + 2
4^th no. = x + x + 2 = 2x + 2
5^th no. = x + 2 + 2x + 2 = 3x + 4
6^th no.,
3x + 4 + 2x + 2 = 26
5x = 20
x = 4
7^th no. = 26 + 3x + 4 = 26 + 3 × 4 + 4 = 42