40 euro= 400centi
1ziar..............................10centi
1revista..........................40centi
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1set(1ziar+1revista).......50centi
1set...................................50centi
xset..................................400centi
_____________________________
x*50=1*400
x=400:50
x=8seturi
1set............1ziar +1revista
8seturi........x ziare+y reviste
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x ziar=8*1=8ziare
y revista=8*1=8reviste