there r 13 days raining.

n 11 morning n 12 afternoons i.e. 11+12 23 times

but for 13 days its once so only 10 time sin one day so ie 1 morning n 1 afternoon so 5 days they went for both the time.

total days 13 days raining n 5 days without it.

13+ 5 18 days

now as we can see that rain is there for only 13 days

so acc to ques they have enjoyed 11 mornings nd 12 afternoon now

these days should contain those days in which they have enjoyed both

afternoon and morning now as in my view they have enjoyed 5 days without rain so they are there for 18 days