In the series 696996676979669779667, how many 9's are immediately preceded by 6 and immediately followed by 7?

The missing number (?) in the following series is : 3, 7, 15, 31, 63, ?

The 6th term in the following series ab² + bc² + cd² + de² + ...... is

Find the next term in the following number series : 2, 7, 24, 77, 238, ……..

In the following number series, a wrong number is given: 2, 6, 16, 38, 84, 168, 368, 750. The wrong number is:

Find the missing number in the following number series. 3, 5, 8, 10, ?, 15, 18, 20