Step 1: First we have to write polynomials in descending order.
$$ \begin{aligned} P(x) &= 5q^7 \\ Q(x) &= -6q^2+9 \\ \end{aligned} $$We can use distribution property to multiply the polynomial by the monomial.
$$ \begin{aligned} \color{blue}{5q^7} \cdot \left( -6q^2+9 \right) &= \color{blue}{5q^7} \cdot \left( -6q^2\right) + \color{blue}{5q^7} \cdot 9 = \\ &= -30q^9+45q^7 \end{aligned} $$