title: How can i solve this error. i want to complete trigger assignment
body: <blockquote>
    <p>Error:Apex trigger AccountAddressTrigger caused an unexpected exception, contact your administrator: AccountAddressTrigger: execution of AfterUpdate caused by: System.FinalException: Record is read-only: Trigger.AccountAddressTrigger: line 6, column 1</p>
  </blockquote>
  
  <p>while solving Create an Apex trigger for Account that matches Shipping Address Postal Code with Billing Address Postal Code based on a custom field.
  I got the above mentioned error
  I had write correct logic but still get the error.</p>