\(a,x+\dfrac{2}{5}=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}-\dfrac{2}{5}\)
\(x=\dfrac{5}{10}-\dfrac{4}{10}\)
\(\Rightarrow x=....\)
\(a,x+\dfrac{2}{5}=\dfrac{1}{2}\\ \Rightarrow x=\dfrac{1}{2}-\dfrac{2}{5}=\dfrac{5-4}{10}=\dfrac{1}{10}\)
\(b,x-\dfrac{2}{5}=\dfrac{1}{7}\\ \Rightarrow x=\dfrac{1}{7}+\dfrac{2}{5}=\dfrac{5+14}{35}=\dfrac{19}{35}\)
\(c,x\cdot\dfrac{3}{4}=\dfrac{9}{20}\\ \Rightarrow x=\dfrac{9}{20}:\dfrac{3}{4}=\dfrac{9}{20}\cdot\dfrac{4}{3}=\dfrac{3\cdot1}{5\cdot1}=\dfrac{3}{5}\)
\(d,x:\dfrac{1}{7}=14\\ \Rightarrow x=14\cdot\dfrac{1}{7}=\dfrac{14}{7}=2\)
\(e,\dfrac{2}{3}-x=\dfrac{1}{5}\\ \Rightarrow x=\dfrac{2}{3}-\dfrac{1}{5}=\dfrac{10-3}{15}=\dfrac{7}{15}\)
\(f,\dfrac{4}{15}:x=\dfrac{12}{25}\\ \Rightarrow x=\dfrac{4}{15}:\dfrac{12}{25}=\dfrac{4}{15}\cdot\dfrac{25}{12}=\dfrac{1\cdot5}{3\cdot3}=\dfrac{5}{9}\)
a, \(x+\dfrac{2}{5}=\dfrac{1}{2}\\ \Rightarrow x=\dfrac{1}{2}-\dfrac{2}{5}\\ \Rightarrow x=\dfrac{5}{10}-\dfrac{4}{10}\\ \Rightarrow x=\dfrac{1}{10}\)
b) \(x-\dfrac{2}{5}=\dfrac{1}{7}\\ \Rightarrow x=\dfrac{1}{7}+\dfrac{2}{5}\\ \Rightarrow x=\dfrac{5}{35}+\dfrac{14}{35}\\ \Rightarrow x=\dfrac{19}{35}\)
c) \(x\times\dfrac{3}{4}=\dfrac{9}{20}\\ \Rightarrow x=\dfrac{9}{20}:\dfrac{3}{4}\\ \Rightarrow x=\dfrac{9}{20}\times\dfrac{4}{3}\\ \Rightarrow x=\dfrac{36}{60}\\ \Rightarrow x=\dfrac{3}{5}\)
a. x + \(\dfrac{2}{5}\) = \(\dfrac{1}{2}\)
\(\Leftrightarrow\dfrac{10x}{10}+\dfrac{4}{10}=\dfrac{5}{10}\)
<=> 10x + 4 = 5
<=> 10x = 1
<=> x = \(\dfrac{1}{10}\)
b. \(x-\dfrac{2}{5}=\dfrac{1}{7}\)
\(\Leftrightarrow\dfrac{35x}{35}-\dfrac{14}{35}=\dfrac{5}{35}\)
<=> 35x - 14 = 5
<=> 35x = 19
<=> x = \(\dfrac{19}{35}\)
c. \(x.\dfrac{3}{4}=\dfrac{9}{20}\)
\(\Leftrightarrow\dfrac{15x}{20}=\dfrac{9}{20}\)
<=> 15x = 9
<=> x = \(\dfrac{9}{15}\)
d. \(x:\dfrac{1}{7}=14\)
\(\Leftrightarrow\dfrac{1}{7x}=14\)
ĐKXĐ: x\(\ne\)0
<=> 14 . 7x = 1
<=> 98x = 1
<=> x = \(\dfrac{1}{98}\)(thỏa mãn)
e. \(\dfrac{2}{3}-x=\dfrac{1}{5}\)
\(\Leftrightarrow\dfrac{10}{15}-\dfrac{15x}{15}=\dfrac{3}{15}\)
<=> 10 - 15x = 3
<=> 10 - 3 = 15x
<=> 15x = 7
<=> x = \(\dfrac{7}{15}\)
f. \(\dfrac{4}{15}:x=\dfrac{12}{25}\)
\(\Leftrightarrow\dfrac{4}{15x}=\dfrac{12}{25}\)
ĐKXĐ: x \(\ne\) 0
<=> 14 . 25 = 12 . 15x
<=> 100 = 180x
<=> x = \(\dfrac{100}{180}=\dfrac{5}{9}\)
a, x + 2/5 = 1/2
\(x+\dfrac{4}{10}=\dfrac{5}{10
}\)
\(x=\dfrac{5}{10}-\dfrac{4}{10}\)
x=1/10
b, x - 2/5 = 1/7
\(x-\dfrac{14}{35}=\dfrac{5}{35}\)
\(x=\dfrac{5}{35}+\dfrac{14}{35}\)
x=19/35
c,x * 3/4 = 9/20
\(x.\dfrac{15}{20}=\dfrac{9}{20}\)
\(x=\dfrac{9}{20}:\dfrac{15}{20}\)
x=5/3
d, x : 1/7 = 14
\(x:\dfrac{2}{14}=14\)
\(x=14.\dfrac{2}{14}\)
x=2
e, 2/3 - x = 1/5
\(\dfrac{10}{15}-x=\dfrac{3}{15}\)
\(x=\dfrac{10}{15}-\dfrac{3}{15}\)
x=7/15
f, 4/15 : x = 12/25
\(\dfrac{20}{75}:x=\dfrac{36}{75}\)
\(x=\dfrac{20}{75}:\dfrac{36}{75}\)
x=5/9
a: Ta có: \(x+\dfrac{2}{5}=\dfrac{1}{2}\)
\(\Leftrightarrow x=\dfrac{1}{2}-\dfrac{2}{5}=\dfrac{5}{10}-\dfrac{4}{10}=\dfrac{1}{10}\)
b: Ta có: \(x-\dfrac{2}{5}=\dfrac{1}{7}\)
\(\Leftrightarrow x=\dfrac{1}{7}+\dfrac{2}{5}=\dfrac{5}{35}+\dfrac{14}{35}=\dfrac{19}{35}\)
c: Ta có: \(x\cdot\dfrac{3}{4}=\dfrac{9}{20}\)
\(\Leftrightarrow x=\dfrac{9}{20}:\dfrac{3}{4}=\dfrac{9}{20}\cdot\dfrac{4}{3}=\dfrac{3}{5}\)
d: Ta có: \(x:\dfrac{1}{7}=14\)
\(\Leftrightarrow x=14\cdot\dfrac{1}{7}=2\)