Hello there!
:)
First, we must find the G.C.F. of 12 and 20:
12: 1, 2, 3, 4, 6, 12.
20: 1, 2, 4, 5, 10, 12
So the G.C.F. of 12 and 20 is 4.
The G.C.F. of 36 and 48:
36: 1, 2, 3, 4, 6, 12, 36.
48: 1, 2, 3, 4, 6, 12, 24, 48.
So 12 is the G.C.F. of 36 and 48.
The G.C.F. of 18, 27 and 45 is:
18: 1, 2, 3, 6, 9, 18.
27: 1, 3, 9, 27.
45: 1, 3, 5, 9, 45.
The G.C.F. of 18, 27 and 45 is 9.
Hope this helps! :)
[tex]GraceRosalia[/tex]