What is the gcf of 30 and 54

The greatest common factor is the biggest whole number that can go into both of them so

first find the factors and collect the ones common to both of them

30=2 times 3 times 5
54=2 times 3 times 3 times 3

the ones common to them both is 2 times 3 which is 6

30|2
15|3
5|5
1

54|2
27|3
9|3
3|3
1