Find the cube root of $729$

The sum of $\frac{1}{2}$ and $\frac{3}{6}$ is _____

If the coefficient of $x$ in the expression $-2x^2{y}^2$ is $m{y}^2$ then the value of $m$ is _____

If the diagonals of a rhombus measure $a$ and $b$, and its area is represented by $\frac{k}{2}$, then the value of $k$ in terms of $a$ and $b$ is _____.

The value of $\left\{\right(-\frac{1}{2}{)}^{-1}{\}}^{-1}$ is _____.