Delete exactly the third row in database

[dedo mraz]

Hello, i know that SELECT * FROM x LIMIT 3,1 will select the trird row. But how can i delete exactly the third row? DELETE FROM x LIMIT 3,1 doesnt work. Here is the table that is created.

CREATE TABLE test (a VARCHAR(15), b VARCHAR(15))
INSERT INTO test VALUES ('x','y')
INSERT INTO test VALUES ('x','AAA')
INSERT INTO test VALUES ('x','y') - i want to delete this row wirhout deleting the first one
INSERT INTO test VALUES ('x','AAA')
INSERT INTO test VALUES ('x','AAA')
INSERT INTO test VALUES ('x','y') - or this one without deleting the first and third one
INSERT INTO test VALUES ('x','AAA')

so now you know how the table looks like, but how do i delete the rows that i marked?

DELETE FROM test WHERE a='x' AND b='y' will delete the first added row.

Any ideas? Thank You.