Here are the steps within Salesforce to create a workflow that will automatically mark all Viewed tasks as complete upon creation.
1) Access Workflow Rules in Salesforce Setup. This is located in Build -> Create -> Workflow & Approvals -> Workflow Rules
2) Create a new Workflow
3) In the dropdown menu, choose the Task Object and click Next.
4) Name the Rule and provide a brief description of the Rule
a) Sample would be Mark Brainshark view receipts complete
5) Under Evaluation Criteria, choose created.*
6) Under Rule Criteria, use the following Criteria:**
a) Field:: Task: Subject
b) Operator:: starts with
c) Value:: VIEWED:
7) Click Save & Next
8) Under Immediate Workflow Actions, click Add Workflow Action and select New Field Update
9) Add a name, unique name, and description to the New Field Update
a) Sample would be Close BNSK Viewed tasks
10) In the Field to Update dropdown menu, select Status and enable the Re-Evaluate Workflow Rules after Field Change.***
11) Under Specify New Field Value, select a specific value, choose Completed from the dropdown menu, and then click Save.
12) Click Done to create the Workflow.
*Note: This is only a suggestion and can be left on the default of "created, and any time it's edited to subsequently meet criteria". The suggestion is only for when it is created so you do not have to worry about the workflow happening in the future after it is created.
*Note: Another rule criteria could be the following in case your company does not want to run a workflow off of the subject of the Task:
a) Field:: Task: Comments
b) Operator:: contains
c) Value:: The link to this presentation is: https://www.brainshark.com
*Note: This is only a suggestion and only suggested if you have other workflows based on Tasks.