Tính:
a) $\frac{3}{5} + \frac{5}{8} =$
b) $\frac{3}{5} - \frac{3}{7} =$
c) $5 \frac{1}{4} \times 5 \frac{2}{5} =$
d) $7 \frac{1}{5} \div 7 \frac{1}{3} =$