The distributive law describes the rules for factoring and multiplying out.

Basically, you did this in elementary school without knowing it.

And that is when calculating tasks from the multiplication tables.

4 x 17 = 4 x (10 + 7) 

4 x 17 = 4 x 10 + 4 x 7

But we can also transform the two-digit number into a difference:

4 x 17 = 4 x (20 - 3)

How it goes on now just the same, you have now surely already understood.