1. The problem asks for the additive inverse of $-\frac{3}{7}$. 2. The additive inverse of a number $x$ is the number that, when added to $x$, results in zero. Mathematically, if $x$ is a number, its additive inverse is $-x$. 3. Given $x = -\frac{3}{7}$, the additive inverse is: $$-\left(-\frac{3}{7}\right) = \frac{3}{7}$$ 4. This means that $-\frac{3}{7} + \frac{3}{7} = 0$, confirming that $\frac{3}{7}$ is the additive inverse. 5. Therefore, the additive inverse of $-\frac{3}{7}$ is $\frac{3}{7}$.