1. The problem asks: When is $x$ equal to 0? 2. This is a simple question about the value of the variable $x$. The variable $x$ is equal to 0 when it is explicitly set or solved to be 0. 3. For example, if you have an equation like $x = 0$, then $x$ is 0. 4. If you have an equation involving $x$, such as $2x + 3 = 3$, you can solve for $x$ by isolating it: $$2x + 3 = 3$$ $$2x = 3 - 3$$ $$2x = 0$$ $$x = \frac{0}{2} = 0$$ 5. So, $x$ is 0 when the equation or condition explicitly leads to $x = 0$. In summary, $x$ is 0 when it is defined or solved to be 0 in a given context.