notam autocare cu x si microbuze cu y,
avem sistemul
1)3x+5y=240
2)4x+6y=320
scadem din ec2-ec1
(4x-3x)+(6y-5y)=(320-240)
obtinem
x+y=80 =>x=80-y
inlocuim in prima ecuatie x=80-y
3(80-y)+5y=240
240-3y+5y=240
240+2y=240
2y=240-240
2y=0
y=0/2
y apartine multimei vide, ecuatia ju are solutii
