3. 8a-15 13-12b -- + --= 2a 3b

3. $$ \frac{8a-15}{2a} + \frac{13-12b}{3b} = \frac{3b(8a-15)+2a(13-12b)}{6ab} = \frac{24ab-45b+26a-24ab}{6ab} = \frac{26a-45b}{6ab} $$

Ответ: $$ \frac{26a-45b}{6ab} $$