2／3a-{1／3-[(3a²-5a+1)]}
=2／3a-{1／3-3a²+5a-1}
=2／3a-1／3+3a²-5a+1
=3a²+2／3a-5a-1／3+1
=3a²-13／3a+2／3
=3*3²-13／3*3+2／3
=27-13+2/3
=14+2/3
=46/3