2/3+6/7-2/3+6/7
=(2/3-2/3)+(6/7+6/7)
=0+12/7
=12/7
1/12+3/8+(5/8+5/12)
=1/12+3/8+5/8+5/12
=(1/12+5/12)+(3/8+5/8)
=1/2+1
=1.5