5. $$ \frac{2a+5b}{ab} - \frac{2a-3b}{ab} = \frac{2a+5b-(2a-3b)}{ab} = \frac{2a+5b-2a+3b}{ab} = \frac{8b}{ab} = \frac{8}{a} $$
Ответ: $$ \frac{8}{a} $$