1. Let's start by writing down the given expression clearly: $$6(3g + h) - 4(3g - h)$$ 2. Next, distribute the numbers 6 and -4 into the parentheses: $$6 \times 3g = 18g$$ $$6 \times h = 6h$$ $$-4 \times 3g = -12g$$ $$-4 \times (-h) = +4h$$ Notice that when distributing -4 through $$-h$$, the two negatives multiply to give a positive. 3. Now rewrite the expression after distribution: $$18g + 6h - 12g + 4h$$ 4. Combine like terms: $$18g - 12g = 6g$$ $$6h + 4h = 10h$$ 5. The simplified expression is: $$6g + 10h$$ 6. So the reason why $$6h - 4h$$ becomes addition in your expression is because the minus sign is distributed through the negative in $$-4(3g - h)$$, turning $$-4 \times (-h)$$ into $$+4h$$. This is a key concept in algebra involving the distribution of negative signs and is why it turns into a plus in this case.