In the Septuagint it states that Methuselah was 167 when he begot Lamech. But that would mean that Methuselah living up to 969 would have survived the flood. The Bible states only 8 people were on the ark. Is there any earlier Old Testament text that gives Methuselah a different age when he begot Lamech?
The copying of numbers in Hebrew is rather problematic, so we need to be a bit cautious about making arguments one way or another about numbers found in the Hebrew text. Having said that, the number of years given in Genesis is consistent with Methusaleh having died before the flood happened. Here is how it works. Lamech lived for 595 years after he gave birth to Noah and Methusaleh lived 782 years after giving birth to Lamech. (taking the numbers at face value, and assuming no copying error). Five hundred years later (an approximation?) Noah gave birth to his three sons. I assume that they were not all born the same year, so the 500 years is an approximation. After this, Noah spent 100 years building the ark before the flood came. That is what the text says, again, assuming that the numbers are to be taken at face value and that there is no copying error. With these numbers in hand, then Methusaleh was dead when the flood began. I get 969 – 187 (birth of Lamech) – 182 (birth of Noah) – 500 (age when Noah gave birth to Ham, Shem and Japheth) – 100 years (to build the ark, before the flood). The result is 969 years – 969 years = 0 years, which implies that either Methuselah had died recently (allowing for a few years over which Noah had his children), or perhaps he even died in the flood.
In this calculation, I am using the numbers in the Masoretic text which, being in Hebrew, is more likely to represent the original than the Septuagint, which was a translation from the Hebrew. Even if we use the Septuagint number, the number of years it took Noah to father the three sons, might allow for Methuselah to die before the flood. I lean toward the Masoretic text.