Finding k from Linear Transformations

Consider the linear equation given by the function $f(x) = 3x - 12$. A second function, $g(x)$, is defined as the transformation of $f(x)$ such that $g(x) = f(x + 2) + k$, where $k$ is a constant integer. If the graph of $g(x)$ intersects the x-axis at the point $(0, 0)$, what is the value of $k$?