Đáp án:

e. \(\dfrac{5}{{12}}\)

Giải thích các bước giải:

\(\begin{array}{l}
a.\dfrac{{3.10 + 35 + 3}}{{70}} = \dfrac{{68}}{{70}} = \dfrac{{34}}{{35}}\\
b. - \dfrac{3}{7} + \dfrac{{15}}{{26}} - \dfrac{6}{{39}} + \dfrac{3}{7}\\
 = \dfrac{{15}}{{26}} - \dfrac{6}{{39}} = \dfrac{{15.39 - 6.26}}{{26.39}}\\
 = \dfrac{{429}}{{1014}} = \dfrac{{11}}{{26}}\\
c.\dfrac{3}{8} - \dfrac{3}{4} + \dfrac{7}{{12}}\\
 = \dfrac{{3.3 - 3.6 + 7.2}}{{24}}\\
 = \dfrac{5}{{24}}\\
d. - \dfrac{2}{9} + \dfrac{5}{{11}} + \dfrac{7}{9}\\
 = \dfrac{5}{9} + \dfrac{5}{{11}} = \dfrac{{100}}{{99}}\\
e.\dfrac{7}{{36}} + \dfrac{8}{9} - \dfrac{2}{3}\\
 = \dfrac{{7 + 8.4 - 2.12}}{{36}}\\
 = \dfrac{{15}}{{36}} = \dfrac{5}{{12}}
\end{array}\)

Bài 1:

a,$\frac{2}{7}$ +$\frac{1}{2}$ - $\frac{-3}{70}$ 

 =$\frac{11}{14}$- $\frac{-3}{70}$ 

 =  $\frac{29}{35}$ 

b,$\frac{-3}{7}$ +$\frac{15}{26}$ -($\frac{6}{39}$ -$\frac{3}{7}$ )

  =$\frac{27}{182}$ - $\frac{-25}{91}$ 
  =  $\frac{11}{26}$

c, $\frac{15}{40}$ +$\frac{-33}{44}$ -$\frac{56}{-96}$ 

=$\frac{3}{8}$ +$\frac{-3}{4}$  -$\frac{-7}{12}$ 

=  $\frac{-3}{8}$ -$\frac{-7}{12}$ 

=$\frac{5}{24}$ 

d,$\frac{-26}{117}$+ $\frac{30}{66}$-$\frac{-7}{9}$ 
=$\frac{-2}{9}$+ $\frac{5}{11}$ -$\frac{-7}{9}$ 

=$\frac{23}{99}$ -$\frac{-7}{9}$ 

=$\frac{100}{99}$ 

e.$\frac{7}{36}$ -$\frac{328}{-369}$ +$\frac{-46}{69}$ 

=$\frac{13}{12}$ +$\frac{-46}{69}$

= $\frac{5}{12}$