Dạng 1:

Bài 1:

a) $\frac{6}{5}$ + (3 + $\frac{-1}{5}$)

= $\frac{6}{5}$ + $\frac{14}{5}$

= 4

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

= $\frac{-3}{5}$ + $\frac{8}{5}$

= 1

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

= $\frac{-3}{5}$ + $\frac{8}{5}$

= 1

d) $\frac{-5}{11}$ + ( $\frac{-6}{11}$ + 1)

= $\frac{-5}{11}$ + $\frac{5}{11}$

= 0 

e) $\frac{-17}{13}$ + ($\frac{25}{101}$ + $\frac{4}{13}$ )

= $\frac{-17}{13}$ + $\frac{729}{1313}$

= $\frac{-76}{101}$ 

Bài 2:

a) $\frac{2}{7}$ + $\frac{5}{7}$ . $\frac{14}{25}$

= $\frac{2}{7}$ + $\frac{2}{5}$

= $\frac{24}{35}$ 

b) $\frac{4}{7}$ : ($\frac{2}{5}$ . $\frac{4}{7}$)

= $\frac{4}{7}$ : $\frac{8}{35}$

= $\frac{5}{2}$ 

c) $\frac{6}{7}$ + $\frac{5}{7}$ : 5 - $\frac{8}{9}$

= $\frac{6}{7}$ + $\frac{1}{7}$ - $\frac{8}{9}$

= 1 - $\frac{8}{9}$

= $\frac{1}{9}$ 

d) $\frac{-5}{7}$. $\frac{2}{11}$ + $\frac{5}{7}$. $\frac{9}{11}$

= $\frac{-10}{77}$ + $\frac{45}{11}$

= $\frac{5}{11}$ 

e) $\frac{5}{9}$ . $\frac{7}{13}$ + $\frac{5}{9}$ . $\frac{9}{13}$ - $\frac{5}{9}$ . $\frac{3}{13}$ = $\frac{35}{117}$ + $\frac{5}{13}$ - $\frac{5}{39}$

= $\frac{80}{117}$ - $\frac{5}{39}$

= $\frac{5}{9}$ 

f) $\frac{-5}{9}$ + $\frac{8}{15}$ + $\frac{-2}{11}$ + $\frac{4}{-9}$ + $\frac{7}{15}$

= $\frac{-1}{45}$ + $\frac{-2}{11}$ + $\frac{4}{-9}$ + $\frac{7}{15}$

= $\frac{-101}{495}$ + $\frac{4}{-9}$ + $\frac{7}{15}$

= $\frac{-107}{165}$ + $\frac{7}{15}$

= $\frac{-2}{11}$ 

g) $\frac{7}{19}$ . $\frac{8}{11}$ + $\frac{3}{11}$ . $\frac{7}{19}$ + $\frac{-12}{19}$

= $\frac{56}{209}$ + $\frac{21}{209}$ + $\frac{-12}{19}$

= $\frac{7}{19}$ + $\frac{-12}{19}$ 

= $\frac{-5}{19}$

Dạng 2

a) x : 4$\frac{1}{3}$ = -2,5

    x : $\frac{13}{3}$ = $\frac{-5}{2}$

    x = $\frac{-5}{2}$ . $\frac{13}{3}$

    x = $\frac{-65}{6}$ 

b) x : $\frac{-3}{5}$ = $\frac{-10}{21}$

     x = $\frac{-10}{21}$ . $\frac{-3}{5}$

     x = $\frac{2}{7}$ 

c) $\frac{2}{3}x$ - $\frac{1}{2}$ = $\frac{1}{10}$

    $\frac{2}{3}x$ = $\frac{1}{10}$ + $\frac{1}{2}$

    $\frac{2}{3}x$ = $\frac{3}{5}$

    x = $\frac{3}{5}$ : $\frac{2}{3}$

    x = $\frac{9}{10}$  

d) $\frac{1}{2}x$ + $\frac{1}{2}$ = $\frac{5}{2}$

     $\frac{1}{2}x$ = $\frac{5}{2}$ - $\frac{1}{2}$

     $\frac{1}{2}x$ = 2

     x = 2 : $\frac{1}{2}$

     x = 4 

e) $\frac{-2}{3}$ - $\frac{1}{3}$. (2x - 5) = $\frac{3}{2}$

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

    $\frac{1}{3}$. (2x - 5) = $\frac{-13}{6}$

    2x - 5 = $\frac{-13}{6}$ : $\frac{1}{3}$

    2x - 5 = $\frac{-13}{2}$ 

    2x = $\frac{-13}{2}$ + 5 

    2x= $\frac{-3}{2}$ 

    x = $\frac{-3}{2}$ : 2

    x = $\frac{-3}{4}$ 

f) $\frac{2}{5}x$ + $\frac{1}{2}$ = $\frac{-3}{4}$

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

    $\frac{2}{5}x$ = $\frac{-5}{4}$

    x = $\frac{-5}{4}$ : $\frac{2}{5}$ 

    x = $\frac{-25}{8}$ 

g) $\frac{1}{3}x$ - 8 = $\frac{1}{2}x$

     $\frac{1}{3}x$ = $\frac{1}{2}x$ + 8

     $\frac{1}{3}x$ = $\frac{17}{2}$

     x = $\frac{17}{2}$ : $\frac{1}{3}$ 

     x = $\frac{51}{2}$ 

h) x - $\frac{1}{4}$ = $\frac{5}{8}$ . $\frac{3}{2}$ 

    x - $\frac{1}{4}$ = $\frac{15}{16}$ 

    x = $\frac{15}{16}$ : $\frac{1}{4}$ 

    x = $\frac{15}{4}$

i)$\frac{3}{4}$ - x = $\frac{1}{5}$ 

   x = $\frac{3}{4}$ - $\frac{1}{5}$ 

   x =$\frac{11}{20}$ 

j) $\frac{7}{2}$ + 2.x = $\frac{-3}{4}$

   2.x = $\frac{-3}{4}$ - $\frac{7}{2}$

   2. x = $\frac{-11}{4}$

   x = $\frac{-11}{4}$ : 2

   x = $\frac{-11}{8}$

k) $\frac{3}{4}$ - x = $\frac{1}{5}$ 

    x = $\frac{3}{4}$ - $\frac{1}{5}$ 

    x =$\frac{11}{20}$ 

l) $\frac{1}{3}$ + $\frac{2}{3}x$ = $\frac{4}{3}$ 

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

   $\frac{2}{3}x$ = 1

   x = 1 : $\frac{2}{3}$

   x = $\frac{3}{2}$

CHÚC BẠN HỌC TỐT!