2/5 + 4/15 = 2/3 + 3/10 = 5/6 - 3/5 = (4/7 + 2/5) - 1/3 =

[tex] \frac{6}{5} [/tex] + [tex] \frac{4}{15} [/tex]
= [tex] \frac{6}{15} [/tex] + [tex] \frac{4}{15} [/tex]
= [tex] \frac{10}{15} [/tex]
= [tex] \frac{2}{3} [/tex]