In which three languages was the sign on Jesus' cross written?

Answer: Hebrew, Latin and Greek

Pilate's notice read 'JESUS OF NAZARETH, THE KING OF THE JEWS' and was written in Hebrew, Latin, and Greek.

“Pilate also had a notice posted on the cross. It read: JESUS OF NAZARETH, THE KING OF THE JEWS. Many of the Jews read this sign, because the place where Jesus was crucified was near the city, and it was written in Hebrew, Latin, and Greek.”— John 19:19-20 (BSB)