7-3/5+2целых 7/9; 9+1целая 3/4-2/5; 6 целых 5/9+3-7/12. Помогите пожалуйста .

1) $7- frac{3}{5} +2 frac{7}{9}$
$7=6 frac{5}{5}$
$6 frac{5}{5} - frac{3}{5} =6 frac{2}{5}$
$6 frac{2}{5} +2 frac{7}{9} =8 frac{2*9+7*5}{45} =8 frac{53}{45} =9 frac{8}{45}$
2) $9+1 frac{3}{4} - frac{2}{5}$
$9+1 frac{3}{4} =10 frac{3}{4}$
$10 frac{3}{4} - frac{2}{5} = frac{43}{4} - frac{2}{5} = frac{5*43}{5*4} - frac{2*4}{5*4} = frac{215-8}{20} = frac{207}{20}=10 frac{7}{y20}$
3) $6 frac{5}{9} +3- frac{7}{12}$
$6 frac{5}{9} +3=9 frac{5}{9}$
$9 frac{5}{9} - frac{7}{12} = frac{9*9+5}{9} - frac{7}{12} = frac{86}{9} - frac{7}{12}$ ]
$frac{4*86}{4*9} - frac{3*7}{3*12} = frac{344}{36} - frac{21}{36} = frac{344-21}{36} = frac{323}{36} =8 frac{35}{36}$