Answer
Write the smallest digits on the left using the larger digits as you move right.
Work Step by Step
Each digit in a number has a place value. The largest place values are on the left, decreasing as the place values move to the right. Therefore, to create the smallest possible number we used the smallest digit ($3$) for the first three place values (left to right), the second smallest digit ($4$) for the next two place values (left to right) and the third smallest digit ($9$) for the last two place values (left to right).
