We can use distribution property to multiply the polynomial by the monomial.
$$ \begin{aligned} \left( x^2-6x-7 \right) \cdot \color{orangered}{x} &= x^2 \cdot \color{orangered}{x} + \left( -6x\right) \cdot \color{orangered}{x} + \left( -7\right) \cdot \color{orangered}{x} = \\ &= x^3-6x^2-7x \end{aligned} $$