Answer:
1
Step-by-step explanation:
Let's look at the first option in this multiple-choice; 18. 18 is divisible by 18, but is not divisible by 35, so that answer isn't right.
What about 3? 3 is divisible by 18, but it isn't divisible by 35. Let's move on.
7 is divisible by 35, but it isn't divisible by 18.
1 is universally divisible by anything. That doesn't mean it is the greatest common factor, but in this case it is, because none of the other options are a factor of both numbers given. Therefore, 1 is divisible by 18.
