There isn't an ID on the casting table so your where clause will actually be filtering on actor.Id
If you are asking this level of question and having this much difficulty you need to go back and study the basics. You query should probably look like
SELECT
a.[name] AS [Actor Name]
FROM
casting AS c
JOIN actor AS a ON a.[id] = c.[actorid]
WHERE
c.[movieid] = 27
(Note this sql is transact specific take out the square brackets and it'll work on most anything (probably))
Charlie
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Msg 3903, Level 16, State 1, Line 1736
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION