4 i 1/7 - 2 i 2/3 = 4 i 3/21 - 2 i 14/21 = 3 i 24/21 - 2 i 14/21 = 1 i 10/21
7 i 1/9 : 2 i 4/5 = 64/9 : 14/5 = 64/9 * 5/14 = 160/63 = 2 i 34/63
[tex]\\4\frac17-2\frac23=4\frac{3}{21}-2\frac{14}{21}=3\frac{24}{21}-2\frac{14}{21}=1\frac{10}{21} \\... \\7\frac19:2\frac45=\frac{64}{9}*\frac{5}{14}=\frac{32*5}{9*7}=\frac{160}{63}=2\frac{34}{63}[/tex]