Answer:
3
Step-by-step explanation:
To find the Greatest common factor (GCF) of 3m-12n we find the highest letters and/or numbers that is a factor of both :
3m-12n
Both have a common factor of 3 :
[tex]\frac{3m-12n}{3} = m-4n[/tex]
m-4n cannot be simplified anymore so the gcf of 3m-12n is 3.
Hope this helped and have a good day