Oracle Stored Procedure ----- PLS-00103: The symbol '/' appears when the following is needed .. Solve

Oracle Stored Procedure ----- PLS-00103: The symbol "/" appears when the following is required .. solve oracle to write a stored procedure: the following error occurs, [SQL] PLS-00103: The symbol "/" in the need of the following: (after a variety of Google Baidu, defining variables in stored procedures does not allow the use of keywords, But I have defined the variable sum, resulting in errors. The compiled code is: [SQL] create or replace procedure avg_sal (result out char) is I number (5); summ number (20); countnum number (20 ); begin I: = 10; while I <40 loop I: = I + 10; select sum (salary), count (*) into summ countnum from emp where deptno = I; result: = summ/countnum; end loop; end;/[SQL] declare I number (5); sum_sal number (20); begin I: = 10; loop exit when (I> 30); select sum (sal)/count (*) into sum_sal from emp where deptno = I; dbms_output.put_line (I | 'average salary: '| sum_sal); I: = I + 10; end loop; end ;/