Query possibile?

USE tempdb;

CREATE TABLE dbo.foo(
ID int NOT NULL PRIMARY KEY,
IDTIPO int NOT NULL,
NUMERO int NOT NULL
);

INSERT dbo.foo VALUES
      (1, 1, 20)
    , (2, 1, 10)
    , (3, 1, 30)
    , (4, 2, 40)
    , (5, 2, 20)
    , (6, 2, 10) 
    , (7, 3, 50) 
    , (8, 3, 40) 
    , (9, 3, 30);

SELECT F.*
FROM dbo.foo AS F
INNER JOIN (
    SELECT
          IDTIPO
        , MIN(NUMERO) AS NUMERO
    FROM dbo.foo
    GROUP BY IDTIPO
) AS Q
ON F.IDTIPO = Q.IDTIPO
AND F.NUMERO = Q.NUMERO;

/* Output:

ID          IDTIPO      NUMERO
----------- ----------- -----------
2           1           10
6           2           10
9           3           30

(3 row(s) affected)

*/

DROP TABLE dbo.foo;