(
1
)
+
(
-
1
)
=
____________________
(
-
2
)
+
(
6
)
=
____________________
(
-
10
)
+
(
21
)
=
____________________
(
-
2
)
+
(
-
6
)
=
-
____________________
(
-
5
)
+
(
0
)
=
-
____________________
(
2
)
+
(
-
7
)
=
-
____________________
(
-
23
)
+
(
25
)
=
2