## Prealgebra (7th Edition)

$0$
$\frac{0}{-1}=0$ We know this, because zero divided by any number equals zero (with the exception of zero divided by zero, which is undefined). (i.e. $\frac{0}{4}=0, \frac{0}{221}=0, \frac{0}{a}=0$ when $a\ne0$)