Because 3 divides evenly into 123 with no remainder.
The factor pairs of 123 are 1 x 123 and 3 x 41
41*3=123
1, 3, 41, 123
Greatest common factor of 81 and 123 is 3.
The greatest common factor of 123 and 321 is 3.
3 x 41 = 123
3 x 41 = 123
123 = 1 x 123, 3 x 41, 41 x 3, 123 x 1
The GCF is 3.
Divide by three. 1, 3, 41, 123
The GCF is 3.
The Greatest Common Factor is 3