a: =-5/9-4/9+8/15+7/15-2/11=-2/11

b: =10/17+7/17-5/13-8/13+11/25

=11/25

c: =(9/12-2/12)*3/2=7/12*3/2=21/24=7/8

d: =(31/10-25/10)*3-2

=3/5*3-2

=9/5-2

=-1/5

\(a,\dfrac{7}{12}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{7}{12}+\dfrac{1}{6}=\dfrac{7}{12}+\dfrac{2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

\(b,\dfrac{8}{9}-\dfrac{4}{15}:\dfrac{2}{5}=\dfrac{8}{9}-\dfrac{4}{15}\times\dfrac{5}{2}=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{2}{9}\)

đùa thì kệ con mẹ mày xàm loz

Đáp án a là 0,75 

Đáp án b: là 0.86222222222

5/8

3/4

\(a)\dfrac{3}{4}.\dfrac{5}{6}=\dfrac{5}{8}\)

\(b)\dfrac{2}{7}:\dfrac{4}{9}=\dfrac{9}{14}\)

\(\dfrac{3}{4}x\dfrac{5}{6}=\dfrac{3x5}{4x6}=\dfrac{15}{24}=\dfrac{5}{8}\)

b) \(\dfrac{2}{7}:\dfrac{4}{9}=\dfrac{2}{7}x\dfrac{9}{4}=\dfrac{18}{28}=\dfrac{9}{14}\)

`7/12 + 3/4 xx 2/9`

`= 7/12 + 6/36`

`= 7/12 + 1/6`

`= 7/12 + 2/12`

`= 9/12`

`= 3/4`

__

`8/9 - 4/15 : 2/5`

`= 8/9- 4/15 xx 5/2`

`= 8/9 - 20/30`

`= 8/9- 2/3`

`= 8/9- 6/9`

`= 2/9`

a)

`7/12+3/4xx2/9`

`=7/12+1/6`

`=7/12+2/12`

`=9/12`

`=3/4`

b)

`8/9-4/15:2/5`

`=8/9-4/15xx5/2`

`=8/9-2/3`

`=8/9-6/9`

`=2/9`

ai làm đúng e tích đúng cho

e) \(\left(\dfrac{-1}{3}\right)\cdot\dfrac{5}{7}=\dfrac{\left(-1\right)\cdot5}{3\cdot7}=\dfrac{-5}{21}\)

f) \(\dfrac{2}{7}:\dfrac{3}{4}=\dfrac{2}{7}\cdot\dfrac{4}{3}=\dfrac{8}{21}\)

\(e.\left(\dfrac{-1}{3}\right).\dfrac{5}{7}=\dfrac{\left(-1\right).5}{3.7}=\dfrac{-5}{21}\\ f.\dfrac{2}{7}:\dfrac{3}{4}=\dfrac{2}{7}.\dfrac{4}{3}=\dfrac{2.4}{7.3}=\dfrac{8}{21}\)

\(C=\dfrac{-5}{7}+\dfrac{-2}{7}+\dfrac{3}{4}+\dfrac{1}{4}+\dfrac{-1}{5}=-1+1-\dfrac{1}{5}=\dfrac{-1}{5}\)

a, \(\sqrt{25}-3\sqrt{\dfrac{4}{9}}=5-3.\dfrac{2}{3}=3\)

b, \(\left(2-\dfrac{5}{3}\right):\left(\dfrac{2}{7}+\dfrac{5}{21}-1\right)\)

\(=\dfrac{1}{3}:\dfrac{6+5-21}{21}\)

\(=-\dfrac{1}{3}.\dfrac{21}{10}\)

\(=-\dfrac{7}{10}\)

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17+18 = 171 nhé

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17+18.  = 171