3,456 in expanded form? 3 thousand 4 hundred and 56? is this right?

Answer 1

I would write this as
3000 + 400 + 50 + 6
Here is a site that explains it rather well.

Answer 2

2+5=7

Answer 3

5+4=9 4+5=9 is commutative is this right?

Answer 4

Maths word form standard form and expand form