Why is a negative divided by a negative a positive?

if we have two negative numbers, -n and -m and we divide them:

(-n)/(-m)

then we can rewrite the quotient as :

(-1)*n/(-1)*m

and...

(-1)/(-1) * n/m

we know that any number divided by itself is 1 by some rule:

so = (-n)/(-m) = n/m which is positive