tinh nhanh( hôn sô): a.(7 4/9+4 7/11)-3 4/9 b.7 5/11-(2 3/7+3 5/11) c.7 5/9+(2 3/4-3 5/9) giup tui voiiii:<<

a) (7$\frac{4}{9}$ + 4$\frac{7}{11}$) - 3$\frac{4}{9}$ 

= ($\frac{67}{9}$ - $\frac{31}{9}$)  + $\frac{51}{11}$

= 4 + $\frac{51}{11}$

= $\frac{44+51}{11}$ = $\frac{95}{11}$

b) 7$\frac{5}{11}$ - (2$\frac{3}{7}$ + 3$\frac{5}{11}$) 

=  $\frac{-17}{7}$ + ($\frac{82}{11}$ - $\frac{38}{11}$) 

= $\frac{-17}{7}$ + 4

= $\frac{-17+28}{7}$ = $\frac{11}{7}$

c) 7$\frac{5}{9}$ + (2$\frac{3}{4}$ - 3$\frac{5}{9}$) 

= $\frac{11}{4}$ + ($\frac{68}{9}$ - $\frac{32}{9}$) 

= $\frac{11}{4}$ + 4

= $\frac{11+16}{4}$ = $\frac{27}{4}$