$\frac{2}{5}\text{m}+\frac{2}{5}\text{m}\cdot 50\%=\frac{2}{5}\text{m}+\frac{2}{5}\text{m}\cdot \frac{50}{100}=\frac{2}{5}\text{m}+\frac{2}{5}\text{m}\cdot \frac{1}{2}=\frac{2}{5}\text{m}+\frac{1}{5}\text{m}=\frac{3}{5}\text{m - długosˊcˊ kroku ojca Antka}$