general rule for multiplication or division between 2 numbers:
if you multiply or divide by:
1. same signs, answer is postive
2. different signs, answer is negative
so we have a -12 and a +9.9 so the answer is negative
then you divide 12 by 9.9
so the answer is negatiive, remember that
then divide as if positive
do
12/9.9
multiply by 10/10
120/99
simplify
120/99
factor out the 3/3
40/33
do the division (you can use calculator)
1.212121212121212121212121212
then it is negative so
-1.212121