12
You'll need 18 straws because it has 18 edges
If the straw were normal and 8.25 inches then it would take 4.772121212121212... straws.
9.
9
12 straws
I need 100 straws.
8 straws.
6
18 straws.
6
6 straws are needed
15 straws are needed
12
Put many straws together to make it stronger
That's going to depend on what shape you're building, which, as far as I can see, you neglected to mention.
16 straws.