1 by 2 addition
2 by 1 subtraction
2 by 2 addition
2 by 2 subtraction
100

8 + 19

27

100

18 - 3

15

100
10 + 15

25

100

90 - 50

40

200

5 + 30

35

200

23 - 5

18

200

34 + 12

48

200

65 - 25

40

300

3 + 58

61

300

34 - 8

26

300

69 + 11

80

300

72 - 18

54

400

6 + 96

102

400

65 - 6

59

400

58 + 43

101

400

38 - 48

Can't do it!

500

9 + 99

108

500

80 - 7

73

500

55 + 28

83

500

91 - 85

6