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\(\dfrac{2}{x}=\dfrac{5}{6}\)

=>\(x=\dfrac{2\times6}{5}=\dfrac{12}{5}\)

nếu đúng thì tim nhé

11 tháng 8 2015

a) \(\frac{3}{2}-\frac{5}{6}:x=\frac{5}{15}-\frac{3}{15}\)

\(\Leftrightarrow\frac{3}{2}-\frac{5}{6}:x=\frac{2}{15}\)

\(\Leftrightarrow\frac{5}{6}:x=\frac{3}{2}-\frac{2}{15}\)

\(\Leftrightarrow\frac{5}{6}:x=\frac{41}{30}\)

\(\Leftrightarrow x=\frac{5}{6}:\frac{41}{30}\)

\(\Leftrightarrow x=\frac{25}{41}\)

b) \(x-\frac{6}{7}.\frac{14}{8}=\frac{1}{2}-\frac{2}{5}\)

\(\Leftrightarrow x-\frac{3}{2}=\frac{1}{10}\)

\(\Leftrightarrow x=\frac{1}{10}+\frac{3}{2}\)

\(\Leftrightarrow x=\frac{8}{5}\)

c) \(x:\frac{6}{5}+\frac{2}{3}=\frac{7}{3}\)

\(\Leftrightarrow x:\frac{6}{5}=\frac{7}{3}-\frac{2}{3}\)

\(\Leftrightarrow x:\frac{6}{5}=\frac{5}{3}\)

\(\Leftrightarrow x=\frac{5}{3}.\frac{6}{5}\)

\(\Leftrightarrow x=2\)

2 tháng 4 2017

huyền ngốc

16 tháng 4 2021

\(a.32,5-3\cdot0,87=32,5-2,61=29,89\)

\(8,5\cdot\left(1\dfrac{1}{2}+\dfrac{4}{4}\right):5=8,5\cdot\left(\dfrac{3}{2}+\dfrac{4}{4}\right):5\\ =8,5\cdot\left(\dfrac{6}{4}+\dfrac{4}{4}\right):5\\ =8,5\cdot\dfrac{10}{4}:5\\ =\dfrac{85}{4}:5\\ =\dfrac{17}{4}\)

\(b.30,96-6,45+14,4:3=30,96-6,45+4,8\\ =29,31\)

\(\dfrac{2}{5}\cdot\left(\dfrac{4}{5}-\dfrac{1}{2}\right)=\dfrac{2}{5}\cdot\left(\dfrac{8}{10}-\dfrac{5}{10}\right)\\ =\dfrac{2}{5}\cdot\dfrac{3}{10}=\dfrac{3}{25}\)

bài 2

\(a.2,5\cdot12,5\cdot8\cdot0,4=\left(2,5\cdot0,4\right)\left(12,5\cdot8\right)\\ =1\cdot100=100\)

b,\(\dfrac{12}{15}\cdot\dfrac{5}{6}\cdot\dfrac{3}{20}\cdot\dfrac{32}{5}=\dfrac{12\cdot5\cdot3\cdot32}{15\cdot6\cdot20\cdot5}\\ =\dfrac{3\cdot4\cdot5\cdot3\cdot4\cdot8}{3\cdot5\cdot2\cdot3\cdot5\cdot4\cdot5}=\dfrac{16}{25}\)

 

Bài 1: 

a) \(32.5-3\cdot0.87=32.5-2.61=29.89\)

\(8.5\cdot\left(1\dfrac{1}{2}+\dfrac{4}{4}\right):5=8.5\cdot\dfrac{5}{2}:5=\dfrac{17}{2}\cdot\dfrac{5}{2}:5=\dfrac{85}{4}\cdot\dfrac{1}{5}=\dfrac{17}{4}\)

a: 5/7+5/4

=20/28+35/28=55/28

b: 3/2-4/6

=9/6-4/6=5/6

c: 5x3/4=15/4

d: 4/6:8=2/3x1/8=2/24=1/12

20 tháng 9 2022

5/7+5/4 =55/28

3/2-4/6=5/6

5x3/4=15/4

4/6:8=1/12

21 tháng 9 2020

                                                            Bài giải

\(\frac{2}{3}+\frac{3}{4}+\frac{4}{5}=\frac{40}{60}+\frac{45}{60}+\frac{48}{60}=\frac{133}{60}\)

\(\frac{8}{5}+\frac{7}{6}+\frac{10}{9}+\frac{1}{2}=\frac{144}{90}+\frac{105}{90}+\frac{100}{90}+\frac{45}{90}=\frac{394}{90}\)

\(\frac{15}{17}-\frac{11}{13}+\frac{3}{26}=\frac{390}{442}+\frac{374}{442}+\frac{51}{442}=\frac{815}{442}\)

\(\frac{9}{12}\text{ x }\frac{4}{3}\text{ : }\frac{8}{5}=\frac{9}{12}\text{ x }\frac{4}{3}\text{ x }\frac{5}{8}=\frac{9\text{ x }4\text{ x }5}{12\text{ x }3\text{ x }8}=\frac{5}{8}\)

\(\frac{4}{5}\text{ x }\frac{15}{8}\text{ : }\frac{5}{7}=\frac{4}{5}\text{ x }\frac{15}{8}\text{ x }\frac{7}{5}=\frac{4\text{ x }15\text{ x }7}{5\text{ x }8\text{ x }5}=\frac{21}{10}\)

26 tháng 4 2021

\(\frac{2}{3}+\frac{3}{4}+\frac{4}{5}=\frac{40}{60}+\frac{45}{60}+\frac{48}{60}=\frac{133}{60}\) 

\(\frac{8}{5}+\frac{7}{6}+\frac{10}{9}+\frac{1}{2}=\frac{144}{90}+\frac{105}{90}+\frac{100}{90}+\frac{45}{90}=\frac{197}{45}\)

\(\frac{15}{17}-\frac{11}{13}+\frac{1}{26}=\frac{390}{442}+\frac{374}{442}+\frac{51}{442}=\frac{815}{442}\)

\(\frac{9}{12}\times\frac{4}{3}:\frac{8}{5}=1:\frac{8}{5}=\frac{5}{8}\)

\(\frac{4}{5}\times\frac{15}{8}:\frac{5}{7}=\frac{3}{2}:\frac{5}{7}=\frac{21}{10}\)

3 tháng 5 2022

bài 5 ta tính tổng cả ba số đi rồi quy đồng tử số là ra có gì đâu

 

14 tháng 10 2017

x + 7/12 = 11/6 : 2/1 

x + 7/12 = 11/12 

        x     = 11/12 - 7/12

        x     = 1/3