Ordering the values of a varchar2 datatype(Oracle)

Hi everybody,
I've a problem of sorting/ordering the values of a varchar2 datatype.
ex.
SQL> select * from test
2 order by project_line;
PROJECT_LINE
--------------------
29/10
29/10-15
29/100
29/100-15
29/50
30/10
value '29/50' shoud have to appear on the 3rd row and not on the 5th.
I'm using Oracle 9i, ver. 9.2.0.5.0
Can anybody help me out.
Thanks in advance,
Bekele, Amsterdam

No response necessary. (already solved by one of my colleagues with a
combination of decode and replace function).