25l lapte........3l smantana, 75l lapte ..........x l smantana , x=75*3 /25=9 l smantana; 180*3/25= 21,6l smantana ; 3*0,5:25=0,06 l ; b ) 25l lapte......3l smantana, x l lapte.........4,5l smantana , x= 25*4,5/3=37,5 l lapte; 25*0,6/3=5litri de lapte ; 25*0,5/3= 4,1(6)l lapte