#### Answer

$y=-\dfrac{1}{2}$

#### Work Step by Step

Using properties of equality, the solution to the given equation, $
\dfrac{1}{5}+y=-\dfrac{3}{10}
$, is
\begin{array}{l}\require{cancel}
\dfrac{1}{5}+y-\dfrac{1}{5}=-\dfrac{3}{10}-\dfrac{1}{5}
\\\\
y=-\dfrac{3}{10}-\dfrac{2}{10}
\\\\
y=-\dfrac{5}{10}
\\\\
y=-\dfrac{\cancel{5}}{\cancel{5}\cdot2}
\\\\
y=-\dfrac{1}{2}
.\end{array}