31.
97-88-39+42=12
32.
49÷(84-91)=49÷(-7)=(-2)
33.
(123-49-83)÷(186-195)=-9÷9=1
34.
5×(74-93)=5×9=45
35.
(12+63-36)÷(-13)=39÷(-13)=(-3)
36.
29/30-5/18×6/25=29/30-1/15=29/30-2/30=27/30
37.
18/7×(4/9+15/18)=18/7×(8/18+15/18)=18/7×23/18=23/7=3 2/7
38.
8/5×3/4+11/8=6/5+11/8=48/40+55/40=103/40=2 23/40
39.(-1/3)×6/5-5/6×3/25=-2/5-1/10=-4/10+(-1/10)=(-5/10)
40.
18/7×4/9+15/14=8/7+15/14=16/14+15/14=31/14=2 3/14