The answer is 12....if your teacher is looking for specifics on the property I would say the commutative property of multiplication (though since this is marked Elementary school I'm not sure if you guys have gotten that far), but if your teacher just wants a general what-kind-of-problem-is-this property, I'd just put down multiplication.....4 x 3 is basic multiplication, it doesn't really fall under a property unless there's more to the problem that you didn't put down in your post :)
Hope this helps!
