Question 105744
36, 72, and 144
Break down each number into its prime factors.
{{{ 36=    2*2*3*3}}}
{{{ 72=  2*2*2*3*3}}}
{{{144=2*2*2*2*3*3}}}
Now look at the numbers that they all have in common. 
{{{36=    highlight(2*2*3*3)}}}
{{{ 72=  2*highlight(2*2*3*3)}}}
{{{144=2*2*highlight(2*2*3*3)}}}
{{{GCF=highlight(2*2*3*3)}}}
{{{GCF=36}}}