Решение:
а) $$\frac{7}{12} + \frac{2}{12} = \frac{7+2}{12} = \frac{9}{12} = \frac{3}{4}$$
б) $$\frac{5}{24} + \frac{17}{24} = \frac{5+17}{24} = \frac{22}{24} = \frac{11}{12}$$
в) $$\frac{8}{39} + \frac{26}{39} = \frac{8+26}{39} = \frac{34}{39}$$
г) $$\frac{43}{75} + \frac{19}{75} = \frac{43+19}{75} = \frac{62}{75}$$
Ответ: а) $$\frac{3}{4}$$, б) $$\frac{11}{12}$$, в) $$\frac{34}{39}$$, г) $$\frac{62}{75}$$