can you check my answers

|-13| - |9| i got 4

|15| - |-3| i got 12

|-12| + |-3| i got : 15

|-31| + |-12| i got: 43

+9 + (+7) i got: 16
-21
18 + 21 i got : 39

-5 +(-13) i got: 7

-18 + (-3) i got: -21

-2 + (+17) i got: 15

15 + (-9) i got: 6

5 + 21 i got 26

-10 + 3 i got: -7

all good except:

-5 +(-13) = -18

btw, what is that -21 stuck in there?
I ignored it