$$\frac{1}{2}-\frac{2}{5}\\\\ $The LCD (Lowest common denominator) is 10 (not doing five because it will give a negative)\\\\$ \\\frac{1\times5}{2\times5}-\frac{2\times2}{5\times2}\\\\ \frac{5}{10}-\frac{4}{10}\\\\ =\;\frac{1}{10}$$
$$\frac{1}{2}-\frac{2}{5}\\\\ $The LCD (Lowest common denominator) is 10 (not doing five because it will give a negative)\\\\$ \\\frac{1\times5}{2\times5}-\frac{2\times2}{5\times2}\\\\ \frac{5}{10}-\frac{4}{10}\\\\ =\;\frac{1}{10}$$