Well done! That's the right answer.
Hint



Test
+
-
=
43
68
25
18
+
-
=
21c
89c
55c
34c
+
-
=
72c
93c
51c
21c
+
-
=
16
82
49
33
+
-
=
24
36
60
12
+
-
=
24
36
60
12
+
-
=
24
36
60
12