You are able to tell at a glance how many job postings are active by looking at your dashboard. You'll see in the Applicant Analytics at a glance section the number of total active vs. total job postings. 

To see which specific job listings are Active and which are Offline, click the box to the right of Filters: in the bar above the job listings on your dashboard page. You can filter by Online, Offline or Archived jobs.

For more information on how to take your job offlineclick here.