Choose the correct answer and Fill in the blanks:
-9+___=0.-9/+9
If we substitute +9 we get
-9++9-9+9=0
Hence, -9++9=0
-4+(___)=-12.-8/+8
0+-5=__.-5/+5
-1--1=__.0/-2
-72--90=_____.+18/-162
-1+___=+5.-6/+6