How would I create a formula to calculate tasks complete (last 30,60,90 days), open, past due by owner similar to this screen shot which comes from the Webinar - "Manage and Track Tickets with Custom App".
You will want to use COUNTIFS formulas for some and other math functions for others.
For example:
Count the number of open tasks assigned to Jane:
=COUNTIFS(Status:Status, "Open", [Assigned To]:[Assigned To], "Jane")
This will look to the Status and Assigned To columns and will count the number of rows where Status is Open and Assigned To is Jane.
% Closed (for row 5):
=([Percent Complete]5 + [Cost to Department]5) / [Cost to Department]5
Smartsheet help center article on formulas: http://help.smartsheet.com/customer/en/portal/articles/775363-using-formulas
Let me know if there is a specific formula you are having trouble with.