[tex]\bf \textit{volume of a rectangular prism}\\\\
V=lwh\quad
\begin{cases}
l=length\\
w=width\\
h=height\\
------\\
l=x+5\\
w=x+4\\
h=x+2
\end{cases}\implies V=(x+5)(x+4)(x+2)
\\\\\\
V=(x^2+9x+20)(x+2)\\\\\\ V=x^3+9x^2+20x+2x^2+18x+40
\\\\\\
V=x^3+11x^2+38x+40[/tex]