Hello there!
The highest common factor, also known as the greatest common factor, or GCF, is the biggest factor that both numbers have in common.
Let's factor out our numbers.
27;
1 x 27
3 x 9
36;
1 x 36
3 x 12
4 x 9
6 x 6
Both of these numbers have these in common:
1, 3, 9.
Since 9 is the highest number in common, it is our GCF or highest common factor.
I hope this helps!