When subtracting with negative numbers, change the problem to an
problem and

Subtracting a number is the same as adding the opposite of the number

Step-by-step explanation:

Subtracting a negative number from a negative number – a minus sign followed by a negative sign, turns the two signs into a plus sign. So, instead of subtracting a negative, you are adding a positive. Basically, - (-4) becomes +4, and then you add the numbers. For example, say we have the problem -2 - –4.