Which pair of numbers have a greatest common factor of 7?

select each correct answer.

7 and 14

28 and 7

21 and 3

7 and 1

The GCF is the number that is a factor of both (or all) of the numbers of a given set and which is the biggest factor of this kind (often the smaller number of the two)

7 and 14 have a greatest common factor of 7.

 28 and 7 also have a GCF of 7, so the first two responses fit.

21 and 3 have a GCF of 3, so that isn't correct.

7 and 1 have a GCF of 1, so that's incorrect as well.

No solution : there is no number of boxes that she bought