[tex] \frac{1}{3} = \frac{5}{15} \\ \frac{2}{5} = \frac{6}{15} \\ \frac{6}{15} + \frac{5}{15} = \frac{11}{15} \\ \frac{15}{15} - \frac{11}{15} = \frac{4}{15} [/tex]