August 25th is Thursday. August 1st is also Thursday (24 days earlier, exactly 3 weeks). So the Thursdays in August are on 1st, 8th, 15th, 22nd, and 29th - five Thursdays total. Since August 1st is Thursday, July 31st was Wednesday, and July 30th was Tuesday. So the Mondays in August are 4th, 11th, 18th, and 25th - four Mondays.