a)
12 h=12*60=720 min
3/5 h=3/5*60=36 min
2460 sec=2460:60=41 min
b)
x-numarul de bacnote de 5 lei
y-numarul de bacnote de 10 lei
stim ca x+y=100 si 5*x+10*y=800, aceste ecuatii formand un sistem. Daca inmultim prima ecuatia cu -5 obtinem -5x-5y=-500 si 5x+10y=800. Daca le adunam obitnem 5y=300 adica y=60 si x=100-60=40
c)
Notam cu x cantitatea de lichid initial si obtinem
[tex]x-x*\frac{1}{3}=150\\\frac{2}{3}*x=150\\x=\frac{150*3}{2}=225 l[/tex]
[tex]capacitate*\frac{3}{4}=225\\capacitate=\frac{4*225}{3}=300l[/tex]
