2x/3+3y/4=1/5 => 40x+45y=12 (1)
5x/6-5y/2=2 => 15x-45y=36 (2)
(1)+(2) => 55x=48 =>
x=48/55 带入 2x/3+3y/4=1/5 解得 y=-28/55
su x=48/55 y=-28/55