#### Answer

$3,334,499$

#### Work Step by Step

Given the numbers $4, 3, 9$ we will use each digit at least two times to write the smallest seven-digit number possible.
The smallest digit is $3$. We will place the smallest digit ($3$) in the three largest valued columns (one-million, 100-thousands, and ten-thousands).
Next, we will place the second smallest digit ($4$) in the next two largest valued columns (thousands and hundreds).
Next, we will place the third smallest digit ($9$) in the next two largest valued columns (tens and ones).
$3334499$
Separate each group of three digits with a comma.
$3,334,499$