Question

How do I do this ? I don’t understand

Answer 1

It's just dividing out the factoring to their simplest form. 
The bold numbers are the answers that go in the circles. 

1. 16 < 8 and 2
    8 < 2 and 4
    4 < 2 and 2

2. 42 < 14 and 3
     14 < 7 and 2

3. 40 < 2 and 20
    20 < 10 and 2
    10 < 2 and 5

4. I'm not able to see the rest of the factoring tree