[tex]\bf \stackrel{GCF~of}{8\qquad \qquad 52}~~ \begin{cases} 8=&\underline{2\cdot 2}\cdot 2\\ 52=&\underline{2\cdot 2}\cdot 13 \end{cases}\qquad \implies \qquad \stackrel{GCF}{\underline{2\cdot 2}}\implies \stackrel{GCF}{4}[/tex]