Trying to create a report that shows me 'Tickets Not Updated in 7 Days'

I'm trying to create a calculated metric for a report that will show me % of tickets that haven't been updated in 7 days. 

I've tried a few queries

COUNT(FILTER([Ticket ID], DATE_DIFF(TODAY(), [Ticket solved - Date]) > 7 AND [Ticket status - Status] != "Closed" AND [Ticket status - Status] != "Solved"))

and this

COUNT(IF (DATE_DIFF(TODAY(), [Ticket solved - Date]) > 7 AND [Ticket status - Status] != "Closed" AND [Ticket status - Status] != "Solved", [Ticket ID], NULL))

and this 

IF (DATE_DIFF(TODAY(), [Ticket solved - Date]) > 7 AND [Ticket status - Status] != "Closed" AND [Ticket status - Status] != "Solved") THEN 1 ELSE 0 ENDIF

Call it something like 'not-updated-tickets' 

I was then going to create another metric Tickets - [Ticket ID]

and finally Result Calculation Metric

(not-updated-ticket / COUNT(Tickets)) * 100

But I keep getting a syntax error already on the first SQL - if anyone has a working example of the report I'm looking for - I'd be happy if you could share. 

Thanks,

T