43 is a Prime number, and 43 and 66 do not share any common factors beyond 1.
Therefore, the only GCF is, informally, one.
The GCF is 66.
The GCF of 30 and 66 is 6.
The GCF is: 6.
The GCF is 3.
The GCF is 6.
The GCF is 3.
The GCF is 66.
The GCF is 1.
The GCF is 3.
The GCF is 11.
The GCF is 6.
The GCF is 1.