\(\frac{12}{-8} = \frac{3 \cdot 4}{-2 \cdot 4} = -\frac{3}{2}\)
\(\frac{a}{a^2} \cdot \frac{y^3}{y} = \frac{1}{a} \cdot y^2 = \frac{y^2}{a}\)
\(-\frac{3}{2} \cdot \frac{y^2}{a} = -\frac{3y^2}{2a}\)
Ответ: \(-\frac{3y^2}{2a}\)