Don't take the Bible so literally. Some parts were not meant to be taken literally at all. The ages of the early patriarchs is one such aspect.
I discuss this in detail in a series of hubs on Genesis: Bible Commentary.
One clue I'll give you here: Genesis 5:2. Adam in this passage isn't an individual, but a tribe -- all of early humanity.
Another clue is that science tells us quite vividly that Homo sapiens have been around for at least 200,000 years. The ages of those early patriarchs need to add up to something at least equaling this figure. Those ages are too short! And I found the factors needed to peg the real age of Homo sapiens all the way back to the beginning of the Adam tribe.