The set {126, 168, 189} has 21 as a common factor.
The set{154, 231} has 11 as a common factor.
Common factor:
If a number m is completely divisible by number n. Then number n will be the one factor of number m.
(a). Given set of number is, {126, 168, 189}
Now check, 21 is a common factor or not.
[tex]\frac{126}{21}=6,\frac{168}{21}=8,\frac{189}{21}=9[/tex]
It is observed that all numbers are completely divisible by 21.
So that , 21 is common factor.
(b). Given set of number is, {154, 231}
[tex]\frac{154}{11}=14,\frac{231}{11}=21[/tex]
It is observed that all numbers are completely divisible by 11.
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