Answer
Slope $=62$
Approximately, there's an increase of 62 billion dollars spent in tourism every year.
Work Step by Step
$y$ is the amount of money spent worldwide on tourism.
$x$ is the year.
Slope $=\frac{\Delta y}{\Delta x}$
Slope $=\frac{798-550}{2007-2003}$
Slope $=\frac{248}{4}$
Slope $=62$
Approximately, there's an increase of 62 billion dollars spent in tourism every year.