Question 300020
The common factor is a number or term, in this case, that evenly divides both terms in your expression.

If I am going to divided 15x^4y and 5x^2y^3 by a factor that will produce a number or term with no remainder, what factor can that be?

It would have to 5x^2y.  This term factors evenly into 15x^4y and 5x^2y^3.

If you don't believe me, try it out.