bancnote de 1 leu =x
bancnote de 5 lei=y
bancnote de 10 lei=z
x+y+z=18
x=y+2z
x+y=8z
x=y+2z⇒18=y+2z+y+z=2y+3z
x+y=8z⇒18=8z+z=9z/:9
z=2⇒x+y=16=2y+2z/:2
y+z=8/-z⇒y=6
x=y+2z⇒x=6+2·2=6+4=10
a)x=10
y=6
z=2
b) x·1+y·5+z·10=10·1+6·5+2·10=10+30+20=60lei
Sper ca te-am ajutat! =)