7+2=9

57+2=50+7+2=52+7=59

^

(50+7)

5-3=2

85-3=80+5-3=77+5=82

^

(80+5)

5+2=7

35+2=30+5+2=32+5=37

^

(30+5)

3+2=5

63+2=60+3+2=62+3=65

^

(60+3)

4-3=1

74-3=70+4-3=67+4=71

^

(70+4)

3+6=9

13+6=10+3+6=16+3=19

^

(10+3)