A question to often confuse or trip-up a year 6 child is -10 – -10… i.e. minus ten take away minus ten.
One way around this is with visuals to remind a child about the number line and how negative numbers work.
Another way is with tricks or memes, such as taking away a negative is the same as adding a positive.
Either way, and whatever works, it is important to know how to use negative numbers in addition, subtraction, multiplication and division as well as in the REAL WORLD – e.g. temperature and money.