Answer:
On top: 3.9
2nd row: 42
3rd row: 12.6
4th row: 12.6
Top of area model:
3 and .9
Explanation:
Long division has a rhythm of four steps. The outside number(divisor) goes into the inside number (dividend, but just a piece of it). Write the answer (quotient) on top. Multiply the top × the outside number. Write it below. Subtract down. Bring down another digit. See image.
The area model is based on length times width. See image.