Here is the passage again:
Bored with the revision of his research essay. Patrick poked the soft front
of his flat-screen monitor, fascinated by its squishy surface.
You chose to use Punctuation Rule 4 to fix the problem:
Participle phrase + , + main clause.
The correction looks like this:
Bored with the revision of his research essay,
Patrick poked the soft front of his flat-screen monitor, fascinated
by its squishy surface.
Well done! You deserve that cyber burger!