Ответ:

  1. \(\frac{12a}{18b}=\frac{2a}{3b}\).
  2. \(\frac{ab}{15b}=\frac{a}{15}\).
  3. \(\frac{xy(a-b)}{xz(a-b)}=\frac{y}{z}\).
  4. \(\frac{ax-bx}{ay-by}=\frac{x(a-b)}{y(a-b)}=\frac{x}{y}\).
  5. \(\frac{xy^2-y^3}{xy-y^2}=\frac{y^2(x-y)}{y(x-y)}=y\).
  6. \(\frac{a^2+2ab+b^2}{3a+3b}=\frac{(a+b)^2}{3(a+b)}=\frac{a+b}{3}\).

Ответ: \(\frac{2a}{3b};\ \frac{a}{15};\ \frac{y}{z};\ \frac{x}{y};\ y;\ \frac{a+b}{3}\).