What is the missing number 97-91-89?

Answer 1

The answer depends on which number is missing, and on the sequencing rule. Using cubic polynomials,

if it the first, it is 107;

if it is the second, 93.666... recurring;

if it is the third, it is 88.333... recurring; and

if it is the fourth, it is 91.

Of course, the rule need not be polynomial!