(a+b+c)/3=25
a+b+c=75
a=b/4
(a+b)/2=25
a+b=50
b/4+b=50
b+4b=200
5b=200
b=40
a=b/4=10
c=75-a-b=75-10-40=25
2. 2x7,2=14,4 lei
2,5x9=22,5 lei
1,5x10,5=15,75 lei
2+2,5+1,5=6 kg
14,4+22,5+15,75=52,65 lei
52,65:6=8,775 lei/kg
3.
(2x350+3x620+5x450)/(2+3+5)=(700+1860+2250)/10=4810/10=481 lei