1)1-9/31 2)2-21/53 3)8-1 39/44 4)7-3 21/23 5)1 4/7 + 2 4/21 6)4 2/3 + 5 4/7 7)9 5/9 + 5...

1) 1 - $\frac{9}{31}$ = $\frac{31}{31}$ - $\frac{9}{31}$ = $\frac{22}{31}$
2) 2 - $\frac{21}{53}$ = 1 $\frac{53}{53}$ - $\frac{21}{53}$ = 1 $\frac{32}{53}$
3) 8 - 1 $\frac{39}{44}$ = 7 $\frac{44}{44}$ - 1 $\frac{39}{44}$ = 6 $\frac{5}{44}$
4) 7 - 3 $\frac{21}{23}$ = 6 $\frac{23}{23}$ - 3 $\frac{21}{23}$ = 3 $\frac{2}{23}$
5) 1 $\frac{4}{7}$ + 2 $\frac{4}{21}$ = 1 $\frac{12}{21}$ + 2 $\frac{4}{21}$ = 3 $\frac{16}{21}$
6) 4 $\frac{2}{3}$ + 5 $\frac{4}{7}$ = 4 $\frac{14}{21}$ + 5 $\frac{12}{21}$ = 9 $\frac{26}{21}$ = 10 $\frac{5}{21}$
7) 9 $\frac{5}{9}$ + 5 $\frac{1}{4}$ = 9 $\frac{20}{36}$ + 5 $\frac{9}{36}$ = 14 $\frac{29}{36}$
8) 6 $\frac{10}{21}$ + 4 $\frac{5}{6}$ = 6 $\frac{20}{42}$ + 4 $\frac{35}{42}$ = 10 $\frac{55}{42}$ = 11 $\frac{13}{42}$
9) 0,8 - $\frac{5}{9}$ = $\frac{8}{10}$ - $\frac{5}{9}$ = $\frac{72}{90}$ - $\frac{50}{90}$ = $\frac{22}{90}$ = $\frac{11}{45}$
10) 0,48 + $\frac{3}{8}$ = $\frac{48}{100}$ + $\frac{3}{8}$ = $\frac{12}{25}$ + $\frac{3}{8}$ = $\frac{96}{200}$ + $\frac{75}{200}$ = $\frac{171}{200}$