(100 - b : 3) × 5 = 250
100 - b : 3 = 250 : 5
100 - b : 3 = 50
b : 3 = 100 - 50
b : 3 = 50
b = 50 × 3
b = 150
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( c : 9 : 3) × 2 = 20
c : 9 : 3 = 20 : 2
c : 9 : 3 = 10
c : 9 = 10 × 3
c : 9 = 30
c = 30 × 9
c = 270
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Am folosit ptr ambele exercitii metoda mersului invers .
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