\(\frac{4}{5}-\frac{1}{a}=\frac{3}{10}\)
\(\frac{1}{a}=\frac{4}{5}-\frac{3}{10}\)
\(\frac{1}{a}=\frac{5}{10}\)
\(\frac{1}{a}=\frac{1}{2}\)
\(=>a=2\)
HT
\(\frac{4}{5}-\frac{1}{a}=\frac{3}{10}\)
\(\frac{1}{a}=\frac{4}{5}-\frac{3}{10}\)
\(\frac{1}{a}=\frac{1}{2}\)
\(\Rightarrow a=2\)