To add \(-\frac{12}{7}\) and \(\frac{3}{14}\), we need a common denominator. The least common multiple of 7 and 14 is 14.
First, we convert \(-\frac{12}{7}\) to a fraction with a denominator of 14:
\[ -\frac{12}{7} = -\frac{12 \times 2}{7 \times 2} = -\frac{24}{14} \]
Now we can add the two fractions:
\[ -\frac{24}{14} + \frac{3}{14} = \frac{-24 + 3}{14} = \frac{-21}{14} \]
We can simplify \(\frac{-21}{14}\):
\[ \frac{-21}{14} = \frac{-3}{2} \]
So, the final result is:
\[ -\frac{3}{2} \]