Answer:
a) 3
b) 11
c) 7
Step-by-step explanation:
The factors of 21 are: 1, 3, 7, 21
The factors of 411 are: 1, 3, 137, 411
A common prime factor is 3.
The factors of 77 are: 1, 7, 11, 77
The factors of 242 are: 1, 2, 11, 22, 121, 242
A common prime factor is 11.
The factors of 56 are: 1, 2, 4, 7, 8, 14, 28, 56
The factors of 63 are: 1, 3, 7, 9, 21, 63
A common prime factor is 7.
