Erin says that the number line represents the expression 1 - 8 and Molly says that it represents the expression 1 + (-8). Who is correct? Only Erin is correct because subtracting a positive means you move to the left. They are both correct because it is moving left and subtracting a positive is the same as adding a negative. Only Molly is correct because adding a negative means you move to the left. They are both incorrect because moving to the left means you are adding a positive number.