Directions:

Identify the number that should replace the question mark in the series below.

73, 81, 92, 106, 123, ?

The correct answer is 143.

To find the number that replaces the question mark, let us analyze the pattern by calculating the differences between consecutive terms in the series:

$81-73=8$

$92-81=11$

$106-92=14$

$123-106=17$

Notice that the differences between consecutive numbers form their own sub-series: 8, 11, 14, 17.

Now, let us find the pattern in these differences (the second-level difference):

$11-8=3$

$14-11=3$

$17-14=3$

The difference increases by 3 at each step. Therefore, the next difference to add to the series is:

$17+3=20$

Finally, adding this difference of 20 to the last given term (123) gives the missing number:

$123+20=143$

Hence, the number that should replace the question mark is 143.