Question

  

Answer 1

18: =>x+11=32+(-11-9)=12

=>x=1

19: =>7-x-7=0

=>x=0

20: =>7+x-8=32

=>x-1=32

=>x=33

Answer 2

18: =>x+11=32+(-11-9)=12=>x=1

19: =>7-x-7=0=>x=0

20: =>7+x-8=32=>x-1=32=>x=33

Answer 3

21 .(-4-x)+(4-15)=-15

<=>-4-x+4-15=-15

<=>-x-15=-15

<=>x=0

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