SQLITE ADD days into Column Using Subquery

Need help with assignment question! Need to use update with a sub-query to add correct days into different rows who match with proper column and row from other table. Trying to update the due date (7 days + checkedOut date) of entries with DVD only. SO far i tried using following code

UPDATE LOAN 
SET (SELECT DUEDATE 
     FROM Media 
     JOIN Item USING (MediaID)  
     JOIN  InventoryItem USING (ItemID) 
     JOIN Loan USING (InventoryItemID) 
     WHERE MediaCode = 'DVD')  =  DATETIME (checkedOut, '+7 days') 

For some reasons it keep giving me error "near "(": syntax error: " when trying to run it. Simply I want to change all the due dates of DVD's to add correctly (7 days) according to checkedout date. Any help will be appreciated.