Help with outputting record with greatest date and added days

I am working on a to do list

I have two fields start_date and days

I want to be able to add days to the start_date and output the highest (oldest) date in the table once this is done

I know how to add the number of days to the start_date using server connect,

I know how to filter the query to get the oldest start_date

I just can not figure out how to output the oldest start_date+days
Not sure if I would need to do the in the query or if it is possible to do it using server connect

I hope this makes sense