Parallel - Determine if all branches are approved?

As noted in the previous comments in most situations you don't need three parallel activities to handle this scenario.  Take a look at this whitepaper on advanced destinations and slots.  In most cases, this will be the easiest way to handle parallel approvals.

http://k2underground.com/files/folders/technical_product_documents/entry20948.aspx

That being said, I have occasionally encountered situations where you really do want approvals on parallel paths.  Activity level variables, like outcomes, are only in scope as long as the activity is executing, so you can't reference them in another activity.  An easy way to do this would be to add a process level data field, like a boolean, that will be set for each path.  Set the initial value to false and only set it to true when the approved condition is met.

In the approved path for each parallel route, add a server code event to an activity after the approval, but before the paths join.  In this code event, add a line of code something like this:

K2.ProcessInstance.DataFields["pathA"].Value = True;

In the activity where you want to join up all parallel paths, add a preceeding rule (right-click | Properties | Preceeding Rule).  This rule will only allow the activity to run when it becomes true.  Set the condition of the preceeding rule to make sure all of the variables for each path are true.