ASV notes on Genesis 11:10-11
Japheth was probably the first born of Noah’s three sons and might have been born when Noah was 500 years. Shem was born when Noah was 502 years and we will now follow the generations of Shem through Abraham.
Shem became 600 years and had Arpachshad. Arpachshad became 438 years and had Shelah. Shelah became 433 years and had Eber. Eber became 464 years and had Peleg. Peleg became 239 years and had Reu. Reu became 239 years and had Serug. Serug became 230 years and had Nahor, the grandfather of Abraham. Nahor became 148 years and had Terah. Terah became the father of Abraham, Nahor and Haran, the first born. Terah became 205 years.
Noah lived 950 years, his son Shem lived 600 years and we see that their ages did decrease down to between 140 and 200 years approximately. Abraham for instance became 175 years.