Răspuns:
l-4ul-5bl=1620
l-1/5*l-1/4*l=162*1/2
l-l/5-l/4=81 (aducem la acelasi numitor)
20l/20-4l/20-5l/20=1620/20
120l-4l-5l=1620
111*l=1620
cantitatea de lapte obtinuta intr-o zi=1620/111
cantitatea de lapte obtinuta intr-o saptamana=(1620*7)/111=11340/111
