Đáp án:

Giải thích các bước giải:

 $a. \frac{2}{5} - (\frac{7}{10} - \frac{3}{5})$

$= \frac{2}{5} - \frac{7}{10} + \frac{3}{5}$

$= \frac{2}{5} + \frac{3}{5} - \frac{7}{10}$

$= 1 - \frac{7}{10}$

$= \frac{3}{10}$

$b. \frac{3}{4} - \frac{2}{5} - (\frac{3}{5} + \frac{3}{4})$

$= \frac{3}{4} - \frac{2}{5} - \frac{3}{5} - \frac{3}{4}$

$= (\frac{3}{4} - \frac{3}{4}) - (\frac{2}{5} + \frac{3}{5})$

$= 0 - 1 = -1$

$c. (\frac{7}{4} + \frac{1}{3}) - (\frac{15}{4} - \frac{2}{3})$

$= \frac{7}{4} + \frac{1}{3} - \frac{15}{4} + \frac{2}{3}$

$= \frac{7}{4} - \frac{15}{4} + (\frac{1}{3} + \frac{2}{3})$

$= \frac{-8}{4} + 1 = -2 + 1 = -1$

$d. (3 - \frac{1}{5}) - (1 + \frac{2}{5}) + (2 + \frac{3}{5})$

$= 3 - \frac{1}{5} - 1 - \frac{2}{5} + 2 + \frac{3}{5}$

$= (3 - 1 + 2) - (\frac{1}{5} + \frac{2}{5} - \frac{3}{5})$

$= 4 - 0 = 4$

$e. (3\frac{1}{2} + 0,25) - (\frac{1}{4} - 3,25 + \frac{1}{2})$

$= \frac{7}{2} + \frac{1}{4} - \frac{1}{4} + \frac{13}{4} - \frac{1}{2}$

$= (\frac{7}{2} - \frac{1}{2}) + (\frac{1}{4} - \frac{1}{4} + \frac{13}{4})$

$= 3 + 3,25 = 6,25$

$f. (2 + \frac{1}{2} + \frac{2}{3} - \frac{3}{4}) - (3 + \frac{1}{4} - \frac{1}{2} - \frac{4}{3})$

$= 2 + \frac{1}{2} + \frac{2}{3} - \frac{3}{4} - 3 - \frac{1}{4} + \frac{1}{2} + \frac{4}{3}$

$= (2 - 3) + (\frac{1}{2} + \frac{1}{2}) + (\frac{2}{3} + \frac{4}{3}) + (-\frac{3}{4} -\frac{1}{4})$

$= -1 + 1 + 2 - 1 = 1$

$g. -(\frac{11}{14} - \frac{8}{19}) + (\frac{3}{14} - \frac{8}{19})$

$= -\frac{11}{14} + \frac{8}{19} + \frac{3}{14} - \frac{8}{19}$

$= (-\frac{11}{14} + \frac{3}{14}) + (\frac{8}{19} - \frac{8}{19})$

$= -\frac{4}{7} + 0 = -\frac{4}{7}$

Đáp án:

Giải thích các bước giải:

 1,⇔$\frac{2}{5}$- $\frac{7}{10}$+ $\frac{3}{5}$= $1$-$\frac{7}{10}$ =$\frac{10}{10}$-$\frac{7}{10}$= $\frac{3}{10}$ 

2,⇔$\frac{3}{4}$- $\frac{2}{5}$- $\frac{3}{5}$- $\frac{3}{4}$=-1 

3,⇔$\frac{7}{4}$+ $\frac{1}{3}$- $\frac{15}{4}$+ $\frac{2}{3}$= -2+1=-1

4,⇔3-$\frac{1}{5}$-1- $\frac{2}{5}$+2+ $\frac{3}{5}$=4 

5,⇔$\frac{7}{2}$+ $\frac{1}{4}$- $\frac{1}{4}$+ $\frac{13}{4}$ -$\frac{1}{2}$=$\frac{6}{2}$+$\frac{13}{4}$=$\frac{12}{4}$+ $\frac{13}{4}$= $\frac{25}{4}$ 

6,2+$\frac{1}{2}$+ $\frac{2}{3}$ -$\frac{3}{4}$ -3-$\frac{1}{4}$+$\frac{1}{2}$+$\frac{4}{3}$ =2+1-3-1+2=1

7,⇔-$\frac{11}{14}$+ $\frac{8}{19}$+ $\frac{3}{14}$-$\frac{8}{19}$= $\frac{-4}{7}$ +0=$\frac{-4}{7}$  

8,⇔$\frac{2}{3}$+ $\frac{3}{4}$-$\frac{4}{5}$+ $\frac{5}{6}$ -$\frac{7}{8}$ +$\frac{9}{10}$+ $\frac{1}{2}$+ $\frac{1}{8}$- $\frac{1}{10}$

    ⇔$\frac{2}{3}$+ $\frac{3}{4}$-$\frac{4}{5}$+ $\frac{5}{6}$-$\frac{3}{4}$+ $\frac{4}{5}$+ $\frac{1}{2}$

    ⇔$\frac{1}{2}$+ $\frac{2}{3}$+ $\frac{5}{6}$

    ⇔$\frac{3}{6}$+ $\frac{4}{6}$+ $\frac{5}{6}$=$\frac{12}{6}$=2