When you have
[tex]4x=\dfrac{2}{5}[/tex]
you can solve the equation by multiplying both sides by 1/4. Then simplify.
[tex]4x\cdot\dfrac{1}{4}=\dfrac{2}{5}\cdot\dfrac{1}{4}\\\\x\cdot\dfrac{4}{4}=\dfrac{2\cdot 1}{5\cdot 4}\\\\x=\dfrac{2}{20}=\dfrac{1}{10}[/tex]
