Number of integer solutions of the equation $x + y + z = 30$ if $x \geq 2$, $y \geq 0$, $z \geq -3$ I am trying to solve a problem using permutation/combination but cannot figure out how to proceed.

Suppose the sum of three variables $x, y, z$ is $30$. If $x\ge2, y\ge0, z\ge-3$, how many integer solutions exist?

I understand that $2\le x\le33, 0\le y\le31, -3\le z\le28$. A simple simulation shows that there are $528$ solutions. However, I am unable to calculate this mathematically. I would like a hint so that I can try this on my own.

We wish to find the number of solutions of the equation
$$x + y + z = 30 \tag{1}$$
in the integers subject to the restrictions that $x \geq 2$, $y \geq 0$, and $z \geq -3$.  
Let $x' = x - 2$, $y' = y$, and $z' = z + 3$.  Then $x', y', z'$ are nonnegative integers.  Substituting $x' + 2$ for $x$, $y'$ for $y$, and $z' - 3$ for $z$ in equation 1 yields
\begin{align*}
x' - 2 + y' + z' + 3 & = 30\\
x' + y' + z' & = 31 \tag{2}
\end{align*}
Equation 2 is an equation in the nonnegative integers.  A particular solution of equation 2 corresponds to the placement of two addition signs in a row of $31$ ones.  For instance, 
$$1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 + 1 1 1 1 1 1 1 1 1 1 +$$
corresponds to the solution $x_1 = 21$, $x_2 = 10$, $x_3 = 0$, while 
$$1 1 1 1 1 1 1 + 1 1 1 1 1 1 1 1 1 1 1 + 1 1 1 1 1 1 1 1 1 1 1 1 1$$
corresponds to the solution $x_1 = 7$, $x_2 = 11$, $x_3 = 13$.  The number of solutions of equation 2 is the number of ways we can place two addition signs in a row of $31$ ones, which is equal to the number of ways we can select which $2$ of the $33$ positions required for $31$ ones and $2$ addition signs will be filled with addition signs.

 $$\binom{31 + 2}{2} = \binom{33}{2} = \frac{33!}{2!31!} = \frac{33 \cdot 32 \cdot 31!}{2 \cdot 1 \cdot 31!} = \frac{33 \cdot 32}{2} = 33 \cdot 16 = 528$$

