I’m confused about this question. I can’t tell whether it’s asked in the context of multiplying by -1 or if it’s in a new context. I’m going to assume a new context, where it’s just asking what happens to the number line in addition.
So when you multiply an input by -1 it’s like you’re rotating the number line around 0 180 degrees.
So when you add 10 to an input, what does that do to the number line? Your input on the number line moves to the right by 10 units, or, you slide the number line to the left by 10 units.