Welcome to the forum! Unfortunately you have posted to the wrong forum.
See that forum title above? The one that says:
SQL Developer (Not for general SQL/PLSQL questions)
Your post has NOTHING to do with sql developer. Also when your instructions are this:
Using the case expression, write a query that displays the grade of all employees based on the value of the column job_id, as per the following data:
What that means is that YOU should write a query. It does NOT mean you should ask someone else to write it for you.
The forums do not provide free coding services.
If you have a problem with a query you have written open a thread in the SQL and PL/SQL forum (if it is for an Oracle DB). SQL and PL/SQL
Before you post there read the FAQ for how to ask a question on the forums and the information you need to provide.
When you post there provide your 4 digit Oracle version, your query, the expected results and the results your query produces. If your query does not produce the expected results ask questions about how to find out what the problem is.