Question 382680
If two numbers have a sum of 6, that means they add up to 6.  So if one is x, then x + (other number) = 6.  Subtract x on both sides, and (other number) = 6-x.
What you wrote is x (a number) and x + 6 (6 more than that number).
Instead, you should have x (a number) and 6 - x (6 minus that number, because together they would add to 6).