The
associative rule is a rule about when it's safe to move parentheses
around. You can remember that because the parentheses determine which
expressions you have to do first--which numbers can associate with each
other. It looks like this:
For addition: (a + b) + c = a + (b + c)
For multiplication: (ab)c = a(bc)
The commutative property is about which operations you can do backward
and forward. You can remember this by thinking of people commuting to
work: they go to work every morning, then they repeat the same operation
backward when they commute home. It looks like this:
For addition: a + b = b + a
For multiplication: ab = ba
Finally, the distributive property tells you what happens when you
distribute one operation against another kind in parentheses. It looks
like this:
a * (b + c) = ab + ac
In other words, the a is "distributed" over the b and c.
Of course, you can make these work together:
a * (b + (c + d))
= a * ((b + c) + d) (by the associative property)
= a * (d + (b + c)) (by the commutative property)
= ad + a (b + c) (by the distributive property)
= ad + ab + ac (by the distributive property again).
Hope this helps.
