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1.
=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1
= 2/5 x (12/3 + 15/3 + 1)
=2/5 x 1
=2/5
2.a=1;2
1) \(\dfrac{11}{12}\times\dfrac{28}{13}-\dfrac{11}{12}\times\dfrac{15}{13}=\dfrac{11}{12}\times\left(\dfrac{28}{13}-\dfrac{15}{13}\right)=\dfrac{11}{12}\times\dfrac{13}{13}=\dfrac{11}{12}\times1=\dfrac{11}{12}\)
Vậy biểu thức trên có kết quả là : \(\dfrac{11}{12}\)
2) \(x+653=87\times11\)
\(x+653=957\)
\(x=957-653\)
\(x=304\)
Vậy `x = 304 `
3) \(\text{70 000 + 800 + 20 + 9}=70829\)
`a, x-2=7/15`
`=>x=7/15 +2`
`=>x= 7/15+ 30/15`
`=>x= 37/15`
`b, 9/20 +x=2/5 +3/20`
`=> 9/20 +x=8/20 +3/20`
`=> 9/20 +x=11/20`
`=>x=11/20-9/20`
`=>x= 2/20=1/10`
x = \(\dfrac{7}{15}\) + 2 = \(\dfrac{37}{15}\)
x = \(\dfrac{2}{5}\) + \(\dfrac{3}{20}\) - \(\dfrac{9}{20}\) = \(\dfrac{1}{10}\)
\(\dfrac{3}{5}x+\dfrac{1}{2}x=\dfrac{11}{15}\)
\(\Leftrightarrow\)\(\dfrac{11}{10}x=\dfrac{11}{15}\)
\(\Leftrightarrow\)\(x=\dfrac{2}{3}\)
\(x\times\dfrac{3}{5}+x\times\dfrac{1}{2}=\dfrac{11}{15}\)
\(x\times\left(\dfrac{3}{5}+\dfrac{1}{2}\right)=\dfrac{11}{15}\)
\(x\times\dfrac{11}{10}=\dfrac{11}{15}\)
\(x=\dfrac{11}{15}\div\dfrac{11}{10}\)
\(x=\dfrac{2}{3}\)
Bài 2:
\(=\dfrac{28}{25}\cdot\dfrac{15}{7}\cdot5=\dfrac{75}{25}\cdot4=12\)
Bài 1:
a: \(x+\dfrac{7}{8}=\dfrac{13}{2}:4=\dfrac{13}{8}\)
nên x=13/8-7/8=6/8=3/4
b: \(x:\dfrac{5}{3}=\dfrac{6}{5}-\dfrac{2}{3}=\dfrac{18-10}{15}=\dfrac{8}{15}\)
nên \(x=\dfrac{8}{15}\cdot\dfrac{5}{3}=\dfrac{8}{9}\)
1)
a)\(\dfrac{20}{30}+\dfrac{9}{30}=\dfrac{29}{30}\)
b)\(\dfrac{16}{24}-\dfrac{15}{24}=\dfrac{1}{24}\)
c)\(\dfrac{12}{63}=\dfrac{4}{21}\)
d) \(\dfrac{5}{6}x\dfrac{3}{4}=\dfrac{15}{24}=\dfrac{5}{8}\)
2)
a)\(x=\dfrac{5}{4}-\dfrac{2}{3}\)
\(x=\dfrac{7}{12}\)
b) \(x=4x\dfrac{3}{5}\)
\(x=\dfrac{12}{5}\)
\(1.x-\dfrac{2}{3}\times\left(x+9\right)=1\)
\(x-\dfrac{2}{3}\times x-6=1\)
\(x\times\left(1-\dfrac{2}{3}\right)=7\)
\(x\times\dfrac{1}{3}=7\)
\(x=21\)
\(2.x-\dfrac{11}{15}=\dfrac{3+x}{5}\)
\(\dfrac{15x}{15}-\dfrac{11}{15}=\dfrac{9+3x}{15}\)
\(15x-11=9+3x\)
\(12x=20\)
\(x=\dfrac{5}{3}\)