Выполните сложение: a) $$2\frac{1}{5} + 3\frac{2}{3}$$; б) $$4\frac{2}{3} + 5\frac{4}{7}$$

a) $$2\frac{1}{5} + 3\frac{2}{3} = \frac{11}{5} + \frac{11}{3} = \frac{11 \cdot 3 + 11 \cdot 5}{15} = \frac{33+55}{15} = \frac{88}{15} = 5\frac{13}{15}$$
б) $$4\frac{2}{3} + 5\frac{4}{7} = \frac{14}{3} + \frac{39}{7} = \frac{14 \cdot 7 + 39 \cdot 3}{21} = \frac{98 + 117}{21} = \frac{215}{21} = 10\frac{5}{21}$$