A = $$\frac{2}{5} – \frac{3}{7}$$ =$$\frac{14}{35} – \frac{15}{35}$$ =$$-\frac{1}{35}$$

B = $$\frac{36}{24} \times \frac{48}{72}=\frac{36\times 48}{24\times 72} $$=$$\frac{36 \times 24 \times 2}{24 \times 36 \times 2}=1$$

C=$$\frac{5}{8} \div\frac{2}{9}$$=$$\frac{5}{8} \times \frac{9}{2}$$ =$$\frac{5 \times 9}{8 \times 2} =\frac{45}{16}$$