{a=2b+3.a=3b+20

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{a=2b+3.a=3b+20{a=2b+3.a=3b+20{a=2b+3.a=3b+202b+3=3b+202b-3b=20-3-b=17b=-17a=2b+3=2*-17+3=-31

{a=2b+3.a=3b+20
{a=2b+3.a=3b+20

{a=2b+3.a=3b+20
2b+3=3b+20
2b-3b=20-3
-b=17
b=-17
a=2b+3=2*-17+3=-31