Joe's age,Joe's sister's age and Joe’s father's age sums up to a century . When son is as old as his father ,Joe's sister will be twice as old as now. When Joe is as old as his father then his father is twice as old as when his sister was as old as her father . Age of her father is?
Mathematics is the supreme judge; from its decisions there is no appeal.
Tobias Dantzig
There is something I don't understand about algebra: It has been around for thousands of years, yet no one has ever found out what the value of "x" or "y" really is.