(3 1/7+2 1/3):3 2/7=(22/7+7/3):23/7=(66/21+49/21):23/7=115/21:23/7=115/21*
7/23=5/3=1 2/3
3 1/*13*(2/9+1 4/5)=40/13*(2/9+9/5)=40/13*(10/45+81/45)=40/13*91/45=56/9=
6 2/9
(13 7/12-10 2/3):2 1/2=(163/12-32/3):5/2=(163/12-128/12):5/2=(163-128)/12:5/2=35/12:5/2=35/12*2/5=7/6=1 1/6