a)
[tex] \frac{3}{4} \times \frac{2}{3} + 2 \frac{4}{5} = \frac{6}{12} + 2 \frac{4}{5} = \frac{1}{2} + 2 \frac{4}{5} = \frac{5}{10} + 2 \frac{8}{10} = 2 \frac{13}{10} = 3 \frac{3}{10} [/tex]
b)
[tex](2 \frac{1}{3} - 1 \frac{3}{4} ) \div \frac{7}{8} = (2 \frac{4}{12} - 1 \frac{9}{12} ) \div \frac{7}{8} = (1 \frac{16}{12} - 1 \frac{9}{12} ) \times \frac{8}{7} = \frac{7}{12} \times \frac{8}{7} = \frac{1}{3} \times \frac{2}{1} = \frac{2}{3} [/tex]
