@lstachniak @MutchmorMath @BryceBeilman @marian_small We use ZERO SUMS. You have two negatives(-)(-) . You have to remove four negatives except you only have two. If you add two zero sums (-)(+) (-)(+) to the two you already have (-)(-)(-)(+)(-)(+) you now have four negatives to remove. Then you're left with two positives.