This insert statement will not work because all of the values that you are inserting need to be wrapped in one set of () or Parentheses. Also you have a date value that is missing the right quote. So the error message told you exactly what the issue is.
Code:
INSERT INTO emp VALUES
(7499),'ALLEN','SALESMAN',7698,'15-AUG-98,1600,NULL,30);
This is what the inserts should look like.
Code:
INSERT INTO emp VALUES
(7499,'ALLEN','SALESMAN',7698,'15-AUG-98',1600,NULL,30);
INSERT INTO emp VALUES
(7521,'WARD','SALESMAN',7698,'26-MAR-96',1550,300,30);
INSERT INTO emp VALUES
(7782,'CLARK','MANAGER',7839,'10-APR-97',1250,NULL,10);
INSERT INTO emp VALUES
(7288,'SCOTT','ANALYST',7566,'14-MAY-99',1300,NULL,20);