Is the underlined clause independent or subordinate?
i wrote the number on a notepad so that i would not forget it.
(underlined is i wrote the number on a notepad )
a.
independent
b.
subordinate

A subordinate clause, or a dependent clause is a group of words that cannot form a sentence.

Now ask yourself, can 'I wrote the number on a notepad' stand alone ? Yes, it can.

Now an independent clause, is a group of words with a subject and a predicate, and it can stand alone as one sentence.

Since 'I wrote the number on a notepad' can stand alone, it is considered as an independent clause.

I hope that makes sense. ^_^