The additive identity property states that the sum of any number and zero is the original number. Zero is called the additive identity because adding it to any number yields the original number. Examples are provided such as 3 + 0 = 3, -7 + 0 = -7. Subtractions can be rewritten as additions by changing the operation to addition and making one addend negative, such as 3 - 15 can be written as -15 + 3. The additive identity property relates because a subtraction with a zero added remains the same, such as 15 - 3 + 0 = 15 - 3.