【1】（5/12-5/16）*4/5+2/3
=5/12×4/5-5/16×4/5+2/3
=1/3-1/4+2/3
=1-1/4
=3/4
【2】8/9÷【4/5÷（3/5-1/4）】
=8/9÷4/5×(3/5-1/4)
=10/9×(3/5-1/4)
=2/3-5/18
=7/18