Answer
$d(Q, R)=12$
Work Step by Step
RECALL:
The distance between the points Q and R on a number line, whose coordinates are q and r, respectively, is given by the formula:
$d(Q, R) = |q-r| \text{ or } d(Q, R) = |r-q|$
Use the formula above, with $q = -1$ and $r=8$, to obtain:
$d(P, R)
\\=|8-(-4)|
\\=|8+4|
\\=|12|
\\=12$
