DRDO Multi tasking staff Model paper 5

The explanation is as follows,
Here S and P is used as a code for - and + respectively. i.e.
14 S 3 P 11 = 22 → 14 - 3 + 11 = 25 - 3 = 22.
11 P 3 S 1 = 13 → 11 + 3 - 1 = 14 - 1 = 13.
Similarly, 16 S 2 P 15 → 16 - 2 + 15 = 31 - 2 = 29.
Hence, 29 is the correct alternative.