I am Full of Holes

I have branches, but no fruit, trunk or leaves. 

What am I?

What has one eye but can’t see?

Where does Friday come before Thursday?

Think of a number

Step 1: Multiply it by 3

Step 2: Add 6

Step 3: Divide by 3

Step 4: Subtract the number chosen in step one from the answer in step 4.

What is the answer?