The ancients didn't mean years by the word "year". They meant time periods. These could be different winters and summers, different seasons, different lunar months or anything else. As far as the patriarchs from Adam to Noah are concerned they were lunar months. Multiply by 19 and divide by 235 to get years.

I quote Pliny the Elder, Natural History, book 7.

"The term and length of mans life is uncertain, not only by reason of the diversity of claimants, but also because the Historians have deliveref such variety of men’s ages, and every man by himself hath a several time limited unto him, at the very day of his nativity. Hesiodus, the first writer (as I take it) who has treated of this argument, and yet like a poet, in his fabulous discourse as touching the age of man, saith forsooth, That a crow lives 9 times as long as we; and the harts or stags 4 times as long as the crow; but the ravens thrice as long as they. As for his other reports as touching the Nymphs and the bird Phœnix, they are more like poetical tales, than historical narrations.

Anacreon the poet maketh report, that Arganthonius king of the Tartessians, lived 150 years: and Cynaras likewise king of the Cyprians, ten years longer. Theopompus affirms, that Epimenides the Gnossian, died when he was 157 years old. Hellanicus hath written, that among the Epians in Ćtolia, there be some that continue full two hundred years: and with him accords Damases; adding moreover, that there was one Pictoreus among them, a man of exceeding stature, mighty and strong withal, who lived 300 years.

Ephorus testifies, that ordinarily the Kings of Arcadia were 300 years old ere they died. Alexander Cornelius writes of one Dando a Sclavonian, that lived 500 years. Xenophon in his treatise of old age, makes mention of a king of the Latines, or as some say, over a people upon the sea coasts, who continued alive 600 years: and because he had not lied long enough already, he goes on still and says, That his son came to 800. All those strange reports proceed from the ignorance of the times past, and for want of knowledge how they made their account: for some reckoned the summer for one year, and the winter for another. There were again, that reckoned every quarter for a year, as the Arcadians, whose year was but three months. Ye shall have some, and namely the Ćgyptians, that count change or new moon, for a year: and therefore no marvel if some of them are reported to have lived 1000 years."

The figures given in the KJV are wrong whereas those given by the Septuagint and by Josepghus are the ones which are the most accurate, a fact which Eusebius also deduced and points out in his Chronicon.

Adam -> Seth 230 @age 19, lived 75
Seth -> Enos 205 @age 17, lived 74
Ebos -> Cainan 190 @age 15, lived 73
Cainan -> Malalel 170 @age 14, lived 74
Malalel -> Jared 165 @age 13, lived 72
Jared -> Enoch 162 @age 13, lived 78
Enoch -> Methusala 165 @age 13, lived 78 (Jasher, 905 lunations)
Methusal -> Lamech 187 @age 14, lived 78
Lamech -> Noah 182 @age 15, lived 60
Noah, lived 77.