Chapter 6, Matrices and Determinants - Section 6.2 - The Algebra of Matrices - 6.2 Exercises - Page 512: 31

$(a). GF$ is defined, view answer in the image below. $(b). GE$ is defined, view answer in the image below.

$(a).GF$ is defined because both are $3×3$ matrices and the rows and columns will match. $(b). GE$ is defined because the columns of $G$ will match with rows of $E$. View image below