If the date of the second Thursday of the month is a perfect square, what is the date of the last Monday of the month?

last Monday is 27

Step-by-step explanation:

perfect square: 4, 9, 16

2nd Thursday is a day >5 and < 14 day from the begining of the month, therefore the only day fit the criteria is 9th of the month.

last Monday is 27

Sun Mon Tue Wen Thu Fri Sat

9 10 11

12 13 14 15 16 17 18

...

26 27