Chapter 6 - Section 6.1 - The Greatest Common Factor and Factoring by Grouping - Exercise Set - Page 427: 12

$6x^4y^3$

The $GCF$ of $ 18,6, $ and $ 12 $ is $ 6 .$ The $GCF$ of $ x^5,x^6, $ and $ x^4 $ is $ x^4 .$ The $GCF$ of $ y^4,y^3, $ and $ y^5 $ is $ y^3 .$ Hence, the $GCF$ of the given expressions, $ 18x^5y^4, 6x^6y^3, \text{ and } 12x^4y^5 ,$ is \begin{array}{l}\require{cancel} 6x^4y^3 .\end{array}