Answer
$d(C, A) = 3$
Work Step by Step
$d(C, A)$ represents the distance between the points C and A on a number line.
If the coordinates of C and A are $c$ and $a$, respectively, then:
$d(C, A) = |c-a|$
Based on the given number line, the coordinates of C and A are 0 and $-3$, respectively.
Use the formula above to obtain:
$d(C, A) = |0-(-3)| = |0+3| =|3| = 3$
Thus,
$d(C, A) = 3$
