1/3-(5/6-2/3)
1.
=1/3-5/6-（-2/3)
=1/3-5/6+2/3
=1/3+2/3-5/6
=1-5/6
=1/6
2.
=2/6-(5/6-4/6)
=2/6-1/6
=1/6