To determine the distance between two numbers on a number line, you can use the formula:
\[ \text{Distance} = |a - b| \]
where \( a \) and \( b \) are the two numbers you're comparing.
In this case, let's use \( a = 6.5 \) and \( b = -7.2 \):
\[ \text{Distance} = |6.5 - (-7.2)| \]
This simplifies to:
\[ \text{Distance} = |6.5 + 7.2| = |13.7| = 13.7 \]
Thus, the distance between 6.5 and −7.2 on a number line is 13.7.