Answer :

[tex]120|\fbox{2}\\..60|\fbox{2}\\..30|\fbox{2}\\..15|3\\....5|\fbox{5}\\....1|\\-------------\\160|\fbox{2}\\..80|\fbox{2}\\..40|\fbox{2}\\..20|2\\..10|2\\....5|\fbox{5}\\....1|[/tex]
[tex]----------\\200|\fbox{2}\\100|\fbox{2}\\..50|\fbox{2}\\..25|\fbox{5}\\....5|5\\....1|[/tex]


[tex]GCF(120;\ 160;\ 200)=2\times2\times2\times5=40[/tex]
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Factors of 120:
1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60,120

Factors of 160:
1, 2, 4, 5, 8, 10,16, 20, 32, 40, 80, 160

Factors of 200:
1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 200

Common Factors:
1, 2, 4, 5, 8, 10, 20, 40

Greatest Common Factor:
40