I find using more descriptive variables helpful in understanding problems like this (even if the help is very slight).
If we define $Y$ to be the amount of money left to the younger son and $O$ to be the amount of money left to the older son, then the equation $ Y + O = 497,500 $ says that the entire inheritance is split between them in some way. The equation $ O = 2Y + 10,000 $ captures the condition that the older son received \10,000 more than twice the amount given to the younger son.
Replacing O$ in the first equation gives $ Y + (2Y + 10,000) = 497,500, $ which you can solve for $Y$ and see $ Y = 162,500. $ So, the younger son received \$162,500. We can now use either equation to find out how much the older son received. I'll use the first one to get $ 162,500 + Y = 497,500 $ and so $ Y = 335,000. $ So, the older son received \335,000.
It would not have been a problem to get a fraction/decimal for one of these values (though we didn't in this case). Banks can handle amounts of money like \0.001, even if there isn't a coin worth so little.