So,
When you write a number in expanded form, you separate each non-zero digit and write it according to its place value.
430,290,100
400,000,000
30,000,000
We don't put anything for the millions place because there are none.
200,000
90,000
100
Then we join each of them with a plus sign.
400,000,000 + 30,000,000 + 200,000 + 90,000 + 100
