51 and 1542 and 2460 and 643 and 34
43 + 34 = 77.
The numbers represent the number of days in each month. The tenth position corresponds to October, which has 31 days.
The first number in each set on the piece of paper corresponds to a month of the year. The second number corresponds to a letter in the name of the month. Hence, Miriam is the suspected kidnapper, as 5-1 corresponds to the first letter of the fifth month (i.e. M), and so forth.
Thursday is not the only day beginning with the letter "T."
The first number corresponds to the number of holes in the letters of each month (September = 5); the second number is the number of vowels in each month (September = 3); and the final number is the number of letters in each month (September = 9). Therefore, September = 539.
With each pair of dominos, the top number is doubled, and the bottom number decreases by 4.