Question

Um reservatório contém 500 litros de água e efetuamos ,sucessivamente as seguintes operacoes retiramos 80 colocamos 45 colocamos 30 retiramos 130 retiramos 80

Answer 1

500-80=420+45=465+30=495-130=365-80 = 285

Answer 2

$\tt \acute{A}gua=a\\\\\\\tt a=500-80+45+30-130-80\\\\\\\tt a=420+45+30-130-80\\\\\\\tt a=465+30-130-80\\\\\\\tt a=495-130-80\\\\\\\tt a=365-80\\\\\\\to \boxed{\tt a=285}$