What is the greatest common factor of 20x and 35y?

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The greatest common factor (GCF) of "20x and 35y" is:  " 5 " .
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The answer is:  " 5 " .
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Consider:  "20x" and "35y" ; 

Each of the TWO (2) terms contains "ONE" (1) [single] variable. The variable within EACH term differs from each other.

As such:  "The greatest common factor (GCF) of "20x" and "35y"  is the:  
             "greatest common factor (GCF) of "20" and "35" ; 
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List the factors for each number:
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20:  1, 2, 4, 5, 10, 20 .

35:  1, 5, 7 , 35.
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The greatest common factor (GCF) of "20x and 35y" is:  " 5 " .
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The answer is:  " 5 " .
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