This is the old idea that you remember for high school algebra.
The important point here is that you are factoring a composite into two primes.
DoodleCat explains it quite well on the worksheet and expands the idea to a general equation that relies on your child knowing how to divide polynomials. But the advanced part is just a preview for today and the problems are fairly simple separation of a polynomial into its simplest factors.
When I went through this part with my own children, I wrote the formulas out on very large papers and taped them to the pocket doors that separate our living room from our dining room. That way my kids could refer to them and have them around to stare at while waiting to be excused from the table after dinner.