28. Сократите дробь: а) a(b−2)/(5(b−2)); б) 3(x+4)/(c(x+4)); в) ab(y+3)/(a²b(y+3)); г) 15a(a−b)/(20b(a−b)).

1. \(\dfrac{a(b-2)}{5(b-2)}=\dfrac a5\).
2. \(\dfrac{3(x+4)}{c(x+4)}=\dfrac3c\).
3. \(\dfrac{ab(y+3)}{a^2b(y+3)}=\dfrac1a\).
4. \(\dfrac{15a(a-b)}{20b(a-b)}=\dfrac{3a}{4b}\).

Ответ: а) \(\dfrac a5\); б) \(\dfrac3c\); в) \(\dfrac1a\); г) \(\dfrac{3a}{4b}\).