draw a triangle put a line down the middle and six lines across in column a the numbers are 5,6,20,3,10,11 and a blank and in column b the numbers are 9,11,39,blank,blank,blank,29

Observe that the numbers in column b are one less than twice column a.

Given:

5 9

6 11

20 39

3 __

10 __

11 __

__ 29

This reduces to:

5 4 9

6 5 11

20 19 39

3 2 5

10 9 19

11 10 21

15 14 29

The middle column was added by me for clarity. You may omit it.