Sum of all nos

In first row=31.

In second row=26 (31-5)

In third row=23 (26-3)

In fourth row=21 (23-2)

He re the no which is subtracting from the sum is decreading by 2,1,0..so next we have to subtract 2-0=2 from the sum.

Fifth row shold be 21-2=19

So the ans should be 5.