8. a) -4 + 0 + \(-\frac{3}{8}\); б) -3 + 0 - \(\frac{2}{3}\).

**Решение:**

**8. a) -4 + 0 + \(-\frac{3}{8}\):**
\[-4 + 0 - \frac{3}{8} = -4 - \frac{3}{8} = -4\frac{3}{8}\]

**Ответ:** -4\(\frac{3}{8}\)

**8. б) -3 + 0 - \(\frac{2}{3}\):**
\[-3 + 0 - \frac{2}{3} = -3 - \frac{2}{3} = -3\frac{2}{3}\]

**Ответ:** -3\(\frac{2}{3}\)