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\(\dfrac{4}{5}\left(\dfrac{2}{3}x-\dfrac{9}{5}\right)-\dfrac{2}{5}\cdot\dfrac{-3}{7}=\dfrac{15}{4}\)
\(\Rightarrow\dfrac{2}{5}\left(\dfrac{2}{3}x-\dfrac{9}{5}\right)-\dfrac{-6}{35}=\dfrac{15}{4}\)
\(\Rightarrow\dfrac{2}{5}\left(\dfrac{2}{3}x-\dfrac{9}{5}\right)+\dfrac{6}{35}=\dfrac{15}{4}\)
\(\Rightarrow\dfrac{2}{5}\left(\dfrac{2}{3}x-\dfrac{9}{5}\right)=\dfrac{15}{4}-\dfrac{6}{35}=\dfrac{501}{140}\)
\(\Rightarrow\dfrac{2}{3}x-\dfrac{9}{5}=\dfrac{501}{140}:\dfrac{2}{5}=\dfrac{501\cdot5}{28\cdot5\cdot2}=\dfrac{501}{56}\)
\(\Rightarrow\dfrac{2}{3}x=\dfrac{501}{56}+\dfrac{9}{5}=\dfrac{2001}{280}\)
\(\Rightarrow x=\dfrac{2001}{280}:\dfrac{2}{3}=\dfrac{2001\cdot3}{280\cdot2}=\dfrac{6003}{560}\)
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\(a,\frac{13}{20}+x=\frac{11}{15}\)
\(x=\frac{11}{15}-\frac{13}{20}\)
\(x=\frac{1}{12}\)
\(b,x+\frac{7}{12}=-\frac{5}{6}\)
\(x=-\frac{5}{6}-\frac{7}{12}\)
\(x=-\frac{17}{12}\)
\(c,\frac{4}{7}x=\frac{9}{8}-0,125\)
\(\frac{4}{7}x=1\)
\(x=1\div\frac{4}{7}\)
\(x=\frac{7}{4}\)
\(\left(d\right)5,5x=\frac{13}{15}\)
\(\frac{11}{2}x=\frac{13}{15}\)
\(x=\frac{13}{15}\div\frac{11}{2}\)
\(x=\frac{26}{165}\)
\(e,x\div\frac{2}{3}=\frac{13}{15}\)
\(x=\frac{2}{3}\times\frac{13}{15}\)
\(x=\frac{26}{45}\)
\(f,-\frac{1}{2}\div\left(x-\frac{1}{3}\right)=-\frac{3}{4}\)
\(x-\frac{1}{3}=-\frac{1}{2}\div-\frac{3}{4}\)
\(x-\frac{1}{3}=\frac{2}{3}\)
\(x=\frac{1}{3}+\frac{2}{3}\)
\(x=1\)
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-15 ( x - 2 ) + 7 ( 3 - x ) = 7
-15x + 30 + 21 - 7x = 7
-15x - 7x = 7 - 21 - 30
-22x = -44
x = ( -44 ) : ( -22)
x = 2
Vậy x = 2
-12 ( x - 5 ) + 7 ( 3 - x ) = 5
-12x + 60 + 21 - 7x = 5
-12x - 7x = 5 - 21 - 60
-19x = -76
x = ( -76 ) : (-19)
x = 4
Vậy x = 4.
# HOK TỐT #
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x+x:0,5+x:0,25+x:0,125=15
(=)\(x+x.2+x.4+x.8=15\)
(=)x.(1+2+4+8)=15
(=)x.15=15
(=)x=1
\(\frac{2}{3}\cdot x-0,125=\frac{15}{8}\)
\(\frac{2}{3}\cdot x=\frac{15}{8}+0,125=\frac{15}{8}+\frac{1}{8}=2\)
\(x=2:\frac{2}{3}=2\cdot\frac{3}{2}=3\)
Vậy x=3
2/3.x - 0,125 = 15/8
2/3.x - 1/8 = 15/8
2/3.x = 15/8 +1/8
2/3.x = 2
x = 2:2/3
x = 3