Code:
select emp_no
from emp
where mgr_no = &&par_emp_no
union
select mgr_no
from emp
where mgr_no >= &&par_emp_no
order by 1 desc;
"&&", in Oracle, requires you to insert value for a parameter "par_emp_no". If you use another DB, see if it needs to be changed.
Also, I'd say that your first example lacks in mgr_no = 150 (which is higher than the parametrized 100).