Answer
Christy Walton's worth exceeded that of Zuckerberg by $13$ x $10^{9}$ dollars.
Work Step by Step
Based on the graph, Christy Walton is worth $26.5$ billion dollars. In the same year, Mark Zuckerberg is worth $13.5$ billion dollars. Hence,
$26.5$ - $13.5$ = $13$ billion dollars
Since $10^{9}$ is equivalent to 1 billion, then Christy Walton's worth exceeded that of Zuckerberg by $13$ x $10^{9}$ dollars.
