Here this is what I have created and this should yield the right result

SQL> desc User_Info
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 FIRST_NAME                                NOT NULL VARCHAR2(30)
 LAST_NAME                                 NOT NULL VARCHAR2(30)
 ADDRESS                                   NOT NULL VARCHAR2(100)
 USER_NAME                                 NOT NULL VARCHAR2(20)
 PASSWORD                                  NOT NULL VARCHAR2(20)

SQL> desc Admission_Code
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CODE                                      NOT NULL NUMBER(38)
 STATUS                                    NOT NULL VARCHAR2(20)

SQL> desc Univ_Code
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CODE                                      NOT NULL NUMBER(38)
 UNIVERSITY                                NOT NULL VARCHAR2(30)

SQL> desc User_Admission_Status
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 USER_NAME                                 NOT NULL VARCHAR2(20)
 UNIV_CODE                                          NUMBER(38)
 ADMISSION_CODE                                     NUMBER(38)

SQL> select a.First_Name, a.Last_Name, a.Address, a.User_Name, b.Status, c.University from User_Info a, Admission_Code b, Univ_Code c, User_Admission_Status d where a.User_Name=d.User_Name and b.Code=d.Admission_Code and c.Code=d.Univ_Code;

no rows selected

Good Luck