First, find the prime factors:
9 = 3*3
2000 = 2*2*2*2*5*5*5
None of the prime factors are shared between the two numbers, so the gcf is 1.
The GCF is 9.
The GCF is 9.
The GCF is 9.
The GCF is 9.
The GCF is 9.
The GCF is 9.
GCF(90, 63) = 9
The GCF is 9.
The GCF is 9.
The GCF is 9.
The GCF is 9.
Since 9 is a factor of 18, it is automatically the GCF.