các bạn giúp mình với sos 5sao ctlhn cảm ơn ạ please

a) $\frac{1}{2}$ - $\frac{-1}{3}$ + $\frac{1}{23}$ + $\frac{1}{6}$ 

= $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{23}$ +$\frac{1}{6}$ 
= ( $\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{6}$ ) + $\frac{1}{23}$ 
= 1 + $\frac{1}{23}$ 
= $\frac{24}{23}$ 
b) ( -0,35) . $\frac{3}{14}$ . ( -3$\frac{5}{7}$ ) . ($\frac{-4}{21}$ )
= ($\frac{-7}{20}$ ) . $\frac{3}{14}$ .($\frac{-26}{7}$) . ( $\frac{-4}{21}$ )
= $\frac{-7.3.-26.4}{20.14.7.21}$ 
= $\frac{13}{245}$ 
c) 2. ( - $\frac{1}{2}$ ). (($\frac{2}{3})^{2}$ ) - 3.(-$\frac{1}{2}){2}$ + $\frac{2}{3}$ + 1
= -1 .$\frac{4}{9}$ - 3. $\frac{1}{4}$ + $\frac{2}{3}$ +1
= -1 . $\frac{4}{9}$ - $\frac{3}{4}$ + $\frac{2}{3}$ +1
= $\frac{-4}{9}$ - $\frac{3}{4}$ + $\frac{2}{3}$ +1
= $\frac{-43}{36}$ + $\frac{2}{3}$ +1
= $\frac{-19}{36}$ + 1
= $\frac{17}{36}$ 
Cho mk 5 sao và tlhn nha ^^