2/5-1/6+2/3
= 2/5+(-1/6+2/3 )
=2/5+(-1/6+4/6 )
=2/5+1/2
=9/10
1-1/4+2/5
= 3/4+2/5
=23/20
1/2+5/6-1/3
=8/6--1/3
=1
8/9-5/9+1/6
=1/3+1/6
=3/6
=1/2
2/5-1/6+2/3
= 2/5+(-1/6+2/3 )
=2/5+(-1/6+4/6 )
=2/5+1/2
=9/10
1-1/4+2/5
= 3/4+2/5
=23/20
1/2+5/6-1/3
=8/6--1/3
=1
8/9-5/9+1/6
=1/3+1/6
=3/6
=1/2