What plus what number equals 41?

40+1

39+2

38+3

37+4

36+5

35+6

34+7

33+8

32+9

31+10

30+11

29+12

28+13

27+14

26+15

25+16

24+17

23+18

22+19

21+20

20+21

19+22

18+23

17+24

16+25

15+26

14+27

13+28

12+29

11+30

10+31

9+32

8+33

7+34

6+35

5+36

4+37

3+38

2+39

1+40

These are all operations with natural numbers. More complicated operations look like these:

23,5+17,5 = 41

-1+42 = 41

etc...