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a/b =0,8 ; 5a+7b/9a-3b=
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Răspuns :

Răspuns:

a/b=0,8=>a=0,8b

(5·0,8b+7b)/(9·0,8b-3b)=

(4b+7b)/(7,2b-3b)=11b/4,2b=11/4,2=11:42/10=11·10/42=55/21