Identify the missing number in the number sequence.
Rule: multiply by 2 and add 5 each time.
4, 13, 31, ____, 139.

The correct answer is: 57

Step by step solution:
Rule: multiply by 2 and add 5 each time.
1st term: 4
2nd term: 4 x 2 + 5 = 13 (given)
3rd term: 13 x 2 + 5 = 31 (given)
4th term: 31 x 2 + 5 = 67
5th term: 67 x 2 + 5 =139 ( given)
Hence, option(a) is the correct option.