To find the distance between two numbers on a number line, you can use the formula for distance, which is the absolute difference between the two numbers:
\[ \text{Distance} = |x_1 - x_2| \]
In this case, let \( x_1 = -18.26 \) and \( x_2 = -2.45 \).
Now, calculate the difference:
\[ -18.26 - (-2.45) = -18.26 + 2.45 = -15.81 \]
Now, take the absolute value of this difference:
\[ \text{Distance} = |-15.81| = 15.81 \]
Therefore, the distance between \( -18.26 \) and \( -2.45 \) on a number line is \( \mathbf{15.81} \).