Răspuns:
a+b=50
5x+5y=50
x+y=10 unde x si y prime intre ele
x=1; y=9=>a=5, b=45
x=3; y=7=>a=15, b=35
x=7; y=3=>a=35, b=15
x=9; y=1=>a=45, b=5
nr sunt : 5si 45 ;15 si 35
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100/100+20/100=120/100
12x/10=450=>12x=4500=>x=4500:12=>x=375 lei pretul initial