Answer:
[tex]\large\boxed{GCF(27,\ 36)=9}[/tex]
Step-by-step explanation:
[tex]\begin{array}{c|c}27&3\\9&3\\3&3\\1\end{array}\\\\27=\boxed3\cdot\boxed3\cdot3\\\\\begin{array}{c|c}45&3\\15&3\\5&5\\1\end{array}\\\\45=\boxed3\cdot\boxed3\cdot5\\\\GCF(27,\ 45)=\boxed3\cdot\boxed3=9[/tex]