if you want to Calcualte for each row % Revenue then you can use.
(([Booking Actual]/[Total Seats])-([Budget Actual]/[Total budget rooms]))/[Budget Actual]/[Total budget rooms] as Revenue.
if you have multiple rows for same ID then you have to use group by function .
let me know if you need something more.
You can use the formula you have mentioned , aggregating the values by ID.
(sum(BookingActual)/sum(Total Seats) - sum(BudgetActual)/sum(Totalbudgetrooms)) / sum(BudgetActual)/sum(Totalbudgetrooms) as [%Revenue]
Group By ID ; ....
Check if this is possible in your data model.