(i) 5, 15 and 25
Factors of 5 are 1 and 5
Factors of 15 are 1, 3, 5 and 15
Factors of 25 are 1, 5 and 25
Therefore, the common factors of 5, 15, and 25 are 1 and 5.
(ii) 2, 6 and 8
Factors of 2 are 1 and 2
Factors of 6 are 1, 2, 3 and 6
Factors of 8 are 1, 2, 4 and 8
Therefore, the common factors of 2, 6 and 8 are 1 and 2.