To determine the distance between two numbers on a number line, you subtract one number from the other and take the absolute value of the result.
In this case, we have the numbers 6.5 and -7.2. The formula for distance \(d\) between two numbers \(a\) and \(b\) is:
\[ d = |a - b| \]
Substituting the values:
\[ d = |6.5 - (-7.2)| \]
This simplifies to:
\[ d = |6.5 + 7.2| \]
Now, we perform the addition:
\[ 6.5 + 7.2 = 13.7 \]
Finally, we take the absolute value:
\[ d = |13.7| = 13.7 \]
Thus, the distance between 6.5 and -7.2 on the number line is \( \boxed{13.7} \).