3. x/3 − (x−2)/5

Приводим дроби к знаменателю 15:

\(\dfrac{x}{3}-\dfrac{x-2}{5}=\dfrac{5x-3(x-2)}{15}=\dfrac{5x-3x+6}{15}=\dfrac{2x+6}{15}=\dfrac{2(x+3)}{15}\).

Ответ: \(\dfrac{2(x+3)}{15}\).