How do you identify an integer and its opposite?

Answer 1

An integer is a whole number. In rational form, it can be expressed as an integer divided by 1. In decimal form, it has either only 0s after the decimal point (or an infinitely recurring sequence of 9s).

To identify its opposite you will need context. All integers have an additive opposite. All non-zero integers have a multiplicative opposite. There are other operations (contexts) that lead to other opposites.

To see how there can be lots of opposites, consider the opposite of a young boy. It can be an old person. Or a female. Or something else if opposites are defined in terms of human/non-human, or living/non-living and so on.