$=\left(\begin{array}{c}5\cdot 3\\ 5\cdot 5\end{array}\right)=\left(\begin{array}{c}15\\ 25\end{array}\right)=\backslash begin\{pmatrix\}5\backslash cdot3\backslash \backslash 5\backslash cdot5\backslash end\{pmatrix\}=\backslash begin\{pmatrix\}15\backslash \backslash 25\backslash end\{pmatrix\}$

$=\left(\begin{array}{c}-1\cdot 3\\ -1\cdot 1\end{array}\right)=\left(\begin{array}{c}-3\\ -1\end{array}\right)=\backslash begin\{pmatrix\}-1\backslash cdot3\backslash \backslash -1\backslash cdot1\backslash end\{pmatrix\}=\backslash begin\{pmatrix\}-3\backslash \backslash -1\backslash end\{pmatrix\}$

$={\displaystyle \left(\begin{array}{c}\frac{7}{9}\cdot 27\\ \frac{7}{9}\cdot \mathrm{22,5}\end{array}\right)=\left(\begin{array}{c}21\\ \mathrm{17,5}\end{array}\right)}=\backslash displaystyle\backslash begin\{pmatrix\}\backslash frac79\backslash cdot27\backslash \backslash \backslash frac79\backslash cdot22\{,\}5\backslash end\{pmatrix\}=\backslash begin\{pmatrix\}21\backslash \backslash 17\{,\}5\backslash end\{pmatrix\}$