Question 988002
<pre>
  18   21   24
   3    9    3
   6    4    8
---- ---- ----
21 26  ?

How you go from 18, 3, and 6 to get 21 is:
1. Find the absolute difference between the second and third numbers 3 and 6, 
   which is |3-6| or 3
2. Add that to the first number 18, and get 21.

How you go from 21, 9, and 4 to get 26 is:
1. Find the absolute difference between the second and third numbers 9 and 4, 
   which is |9-4| or 5
2. Add that to the first number 21, and get 26.

So that's the pattern, so with the numbers 24, 3, and 8, we:

1. Find the absolute difference between the second and third numbers 3 and 8,
   which is |3-8| or 5.
2. Add that to the first number 24, and get 29.

Edwin</pre>