How did the brothers justify entering Egypt via ten different gates?
Rashi and Ramban #1 (11): Refer to 42:9:3:3*
Ramban #2 (11): Alternatively, Yosef initially accused them of entering in 10 different gates and then meeting together - a sign that they were spies. The brothers replied that they met together because they were brothers. And in answer to his question why they entered in ten different gates, they replied that they were looking for their missing brother. 1
Seforno: Seeing as their father lived in Cana'an, Yosef would be able to check with him and with his neighbors on everything that they had told him.
And the Torah does not bother to provide us with all their arguments and counter-arguments (Ramban).