Ok, so a subject is the "what" of a sentence and a verb is the action. I'll explain using #1. To find a subject, all you need to do is restate the sentence in a question. So, for #1, your question would be, "What started last week?" and the answer is the trouble. That would be your subject. To find a verb, just find an action. In #1, the action is began. I hope these tips helped.