\(\Rightarrow\dfrac{5}{4}-\dfrac{1}{4}x=\dfrac{3}{10}x-\dfrac{2}{5}\)
\(\Rightarrow\dfrac{5}{4}+\dfrac{2}{5}=\dfrac{3}{10}x-\dfrac{1}{4}x\)
\(\Rightarrow\dfrac{33}{20}=\dfrac{11}{20}x\)
\(\Rightarrow x=\dfrac{33}{20}\div\dfrac{11}{20}\)
\(\Rightarrow x=3\)
\(1\dfrac{1}{4}-x\dfrac{1}{4}=x\cdot30\%\cdot\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{5}{4}-x\dfrac{1}{4}=x\cdot\dfrac{3}{10}-\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{5}{4}-\dfrac{1}{4}x=\dfrac{3}{10}x-\dfrac{2}{5}\)
\(\Leftrightarrow25-5x=6x-8\)
\(\Leftrightarrow-5x-6x=-8-25\)
\(\Leftrightarrow-11x=-33\)
\(\Leftrightarrow x=3\)
Vậy x = 3
\(1\dfrac{1}{4}-x\dfrac{1}{4}=x\times30\%\times\dfrac{2}{5}\)
\(\Rightarrow\dfrac{5}{4}-x\times\dfrac{1}{4}=x\times\dfrac{3}{10}-\dfrac{2}{5}\)
\(\Rightarrow\dfrac{5}{4}\)\(-\dfrac{1}{4}x=\)\(\dfrac{3}{10}x-\dfrac{2}{5}\)
\(\Rightarrow25-5x=6x-8\)
\(\Rightarrow-5-6x=-8-25\)
\(\Rightarrow-11x=-33\)
\(\Rightarrow x=3\)
vay x \(=\)3
giúp mk voi a . cam ơn ban 