1/3 x + 3/4 y = 5/12 .(1)
2/3 x - 5/6 y = -1/3 .(2)
去分母：
4x+3y = 4 .(3)
4x-5y = -2 .(4)
(3)-(4)得：
8y=6
y=3/4
4x+3*3/4=4
4x=7/4
x=7/16