Question

roberto says that the opposite of a certain integer is -5.cindy concludes that the opposite of an integer is always negative.explain cindy's error

Answer 1

Integers are set of whole numbers and their counterparts, for example:

..., -3, -2, -1, 0, 1, 2, 3, ...

If the given integer is below 0, then its opposite will be positive. Let's check it on the example:
 
Opposite of 5 is -5 (so Cindy is right here)
But opposite of -5 is 5 (so she's wrong)