Answer :
so the greatest common factor is found by finding the factors and finding which ones are in both groups so exg (greatest common factor of 20 and 8 is 4 because 20:4*5 and 8=4*2 so 4 is the greastest common factor so )
90=3*3*2*5
33=11*3
the greatest common factor is 3
90=3*3*2*5
33=11*3
the greatest common factor is 3