3 1/7 : 2 1/3 : 3 2/7=22/7 * 3/7 * 7/23=(22*3)/(23*7)=66/161 3 1/13 *(2/9+1 4/5)=70/13 * (10/45+1 36/45)=70/13 * 2 1/45=70/13 * 91/45=98/9=10 8/9 (13 7/12 - 10 2/3) : 2 1/2=(13 7/12 - 10 8/12) * 2/5=2 11/12 * 2/5=35/12 * 2/5=7/6=1 1/6 5 13/20 :(8 2/15 - 3/5)=113/20 :(8 2/15 - 9/15)=113/20 : 7 8/15=113/20 * 15/113=3/5
