2/5=2/10+k so at this equation what does k=?
K + 2/10 = 2/5K = -2/10 + 2/5K = -2/10 + 4/10K = 2/10K = 1/5
\(\frac{2}{5}= \frac{2}{10}+k\) ⇒ \(\frac{2}{5}= \frac{2\div2}{10\div2}+k\)\(\frac{2}{5}= \frac{1}{5}+k\) ⇒ \(k= \frac{2}{5}- \frac{1}{5}\)\(\boxed { k= \frac{1}{5} }\)
