Is 22 divisible by 2, 4, 5, 7, and/or 9?
22/2=11
22/4=5.5
22/5=4.4
22/7=3.142
22/9=2.444
Your answers would be 2 only.

Is 22 divisible by 11?
Yes 22/11=2

What can be multiplied to get 25?
(1, 25) (5, 5)
1, 5, 25

Factor tree of 12
12
2 and 6
2 and 3
2^2 times 3

Greatest Common Factor of 18 and 21
18 (1, 18) (2, 9) (3, 6)
21 (1, 21) (3, 7)
GCF= 3