The greatest common factor of 12 and 90 is 6.
Greatest Common Factors are the largest shared factors between 2 or more numbers.
The factors of 12 and 90 are...
12: 1,2,3,4,6,12
90: 1,2,3,5,6,9,10,15,18,30,45,90
Thus meaning the GCF is 6.
I hope this helps!