SQL & PL/SQL

DDL-table name(200,000 data) sheet2; Inv_num number(10), Price varchar2(20)

Inv_num	price
9606	X
9613	X
9620	X
9644	X
9668	$34.56 
6401	X
6401	$ 52.32
4720	X
4720	$ 539.03
4737	$ 924.05
4737	X
4782	X
4782	$ 89.40

I want to have the following result(not duplicated record + remove one of duplicated record with price 'x');

Inv_num	price
9606	X
9613	X
9620	X
9644	X
9668	$34.56 
6401	$ 52.32
4720	$ 539.03
4737	$ 924.05
4782	$ 89.40

I did it but it is too slow, would you revise my query thanks

SELECT  Inv_num,price

FROM Sheet2
where Sheet2.Inv_num  in(
SELECT Sheet2.Inv_num  FROM Sheet2 where Sheet2.Inv_num in(
SELECT Sheet2.Inv_numFROM Sheet2
GROUP BY Sheet2.Inv_num HAVING (((Count(Sheet2.Inv_num))>1)))) and Sheet2.price <>'x'
union
SELECT Inv_num,price

FROM Sheet2
where Sheet2.Inv_num not  in(
SELECT Sheet2.Inv_num  FROM Sheet2 where Sheet2.Inv_num in(
SELECT Sheet2.Inv_num FROM Sheet2
GROUP BY Sheet2.Inv_num
HAVING (((Count(Sheet2.Inv_num))>1))))

thanks in advance