 Since both right hand sides are equal to \(x\) we can infer \(2y = y^2 /2\). It is tempting to divide both sides by \(y\), but what if \(y = 0\)? In fact \(y = 0\) is one solution, for which \(x = 2y = 0\) as well, corresponding to Xavier and Yvonne both being newborns. Setting that solution to one side we can now look for solutions in which \(y\) is not zero by dividing both sides by \(y\). This yields \(y = 4\), in which case \(x = 2y = 8\). So now we have a second solution in which Xavier is eight years old and Yvonne four.