Curated OER
How Do You Rewrite Subtraction as Addition?
A look at how to write a subtraction problem as an addition problem. The first value stays the same and the second value becomes the opposite value which is added to the first.
Khan Academy
Khan Academy: Adding Integers With Different Signs
Adding integers with different signs.
Khan Academy
Khan Academy: Why Subtracting a Negative Equivalent to Adding a Positive
Intuition as to why subtracting a negative number is equivalent to adding the absolute value of that number