A number or expression multiplied three times can be written as a cube, that is a power with the exponent $3.$ $$\begin{array}{rl}3\cdot 3\cdot 3& =3^3\\ x\cdot x\cdot x& =x^3\\ (a+b)(a+b)(a+b)& =(a+b{)}^3\end{array}$$