Solution:
He spent 05/05/06 to 20/05/06 at his Nani's place.
As the month and year are the same for his stay, we need to find only the difference between the days.
[ 1 Mark ]
Number of days between 05 May to 20th May = 20 -05 = 15
He stayed there for 15 days. [ 1 Mark ]