1) 2/7+3/7=5/7
2) 5/12+2/3=
=5/12+8/12=13/12
3) 19/24-1/12=
=19/24-2/24=17/24
4) 17/32-5/16=
=17/32-10/32=7/32
5) 2/7×3/4=
=1/7×3/2=3/14
6) 12/35×5/14=
=6/5×1/7=6/35
7) 7/8:2/20=
=7/8:1/10=
=7/8×10=
=7/4×5=35/4
8) 24/27:12/54=
=8/9:2/9=
=8/9×9/2=4
