If the 10th term of the sequence a, a - b, a - 2b, a - 3b, ...... is 20 and the 20th term is 10, then the xth term of the series is:

The sum of 4 arithmetic means (AMs) inserted between 3 and 23 is:

If the 7th term and 12th term of an arithmetic progression are 34 and 59 respectively, then its 15th term is:

If two geometric means G1 and G2 are inserted between 3 and 75, then G2 is equal to: