Addition always follows the same three rules, no matter what numbers you use. Once you know them, you can add faster — and later, they're the reason algebra tricks actually work.
You can add two numbers in either order and get the same sum. "Commute" means to travel back and forth — the numbers can swap places and the answer doesn't change.
When you add three or more numbers, it doesn't matter which two you add first — the total comes out the same. "Associate" means to group together, so this is about which numbers team up first.
Any number plus zero stays exactly the same. Zero is called the additive identity because adding it never changes a number's identity.
There's a fourth idea worth knowing: every number has an opposite that adds with it to make zero — like 8 + (−8) = 0. You'll see this a lot more in the Positive & Negative Numbers unit.
Eight questions mixing all three properties — identify which one is being used, or fill in the missing number.