1. x = cantitatea de solutie 50% == > acid pur in aceasta solutie = 50x/100
2. y = canitatea de sol. 35% ==> acid pur = 35y/100
x+y = 10 kg 42% ==> 42 x 10 : 100 = 4,2 kg acid pur
50x / 100 + 35y / 100 = 4,2 ==> 50 x + 35 y 420
x+y = 10 ==> x = 10 - y
50(10-y) +35y = 420 ==> 500-50y+35y = 420 => 15 y = 80 ==y= 5,33 kg
x = 10 - 5,33 = 4,66