Underline them: 6,4,1,2,2,8,7,4,2,1,5,3,8,6,2,2,1,4,1,3,5,8,6 Answer: There are five. (6,4), (4,2), (5,3), (8,6) and (8,6) Note: We did not underline (1,3) or (3,5) because their difference is 1-3 = 3-5 = -2, not 2. To find the difference between two numbers, it's always "first minus second", never "second minus first". Edwin