850 l : 5 l = 170 bidoane
350 l : 5 L = 70 bidoane consumate in I saptamana
300 l : 5 l = 60 bidoane consumate in a II-a saptamana
70 bidoane consumate in I saptamana + 60 bidoane consumate in a II-a saptamana = 130 bidoane
170 bidoane - 130 bidoane = 40 bidoane ramase
40 bidoane : 2 = 20 ladite