Following are a number of back-translations of Mark 9:28:

• Uma: “After that, Yesus and his disciples left there and entered a house. When they had entered the house, they began to ask Yesus, they said: ‘Teacher, why were we (excl.) unable to expel that evil-spirit earlier?'” (Source: Uma Back Translation)
• Yakan: “When Isa had entered the house, his disciples asked him alone (lit. they-they only), they said, ‘Why couldn’t we (excl.) cast out the demon?'” (Source: Yakan Back Translation)
• Western Bukidnon Manobo: “And when Jesus and company had returned to the house where they were staying and no other people were there, just them, his disciples asked him, they said, ‘Why couldn’t we drive away the demon?'” (Source: Western Bukidnon Manobo Back Translation)
• Kankanaey: “When plural Jesus entered the house where they were staying, and they were alone, his disciples asked him, ‘Why were we (excl.) not able to cause-that evil-spirit -to-leave?'” (Source: Kankanaey Back Translation)
• Tagbanwa: “When Jesus had gone into the house, his disciples asked him privately. They said, ‘Why was it that we couldn’t drive out that evil spirit which was possessing/causing-madness?'” (Source: Tagbanwa Back Translation)