[1※（2※3）]—[（1※2）※3]
=[[1※（2²/3]—[（1²/2）※3]
=[1※4/3]—[1/2※3]
=[1²/4/3]—[（1/2)²/3]
=3/4-1/4/3
=3/4-1/12
=2/3