Answer
$$x= -4+t, \quad y= 9+8t.$$
Work Step by Step
Since the slope $m=8$, then we have $s/r=8$ so take $r=1$ and $s=8$. Then, the parametric equations are
$$x=a+rt=-4+t, \quad y= b+st=9+8t.$$
That is,
$$c(t)=(x(t),y(t))=(-4+t,,8t+9).$$