It should be a geometric progression with common ratio of 0.5 Every successive term should be half of the term just before it. Hence, 34 is the odd one out. It should be 28 in its place.
? should be 7 i.e. the first number at the start of fourth term Similarly 23-15 = 8 15-11 = 4 11-? = 2 ? should be 9 i.e. the term at the center of fourth term