Step 1: First we have to write polynomials in descending order.

$$ \begin{aligned} P(x) &= 20x-3 \\ Q(x) &= 2x+5 \\ \end{aligned} $$

In this example we are multiplying two binomials so FOIL method can be used.

$$ \begin{aligned} \left( \color{blue}{ 20x-3}\right) \cdot \left( \color{orangered}{ 2x+5}\right) &= \underbrace{ \color{blue}{20x} \cdot \color{orangered}{2x} }_{\text{FIRST}} + \underbrace{ \color{blue}{20x} \cdot \color{orangered}{5} }_{\text{OUTER}} + \underbrace{ \left( \color{blue}{-3} \right) \cdot \color{orangered}{2x} }_{\text{INNER}} + \underbrace{ \left( \color{blue}{-3} \right) \cdot \color{orangered}{5} }_{\text{LAST}} = \\ &= 40x^2 + 100x + \left( -6x\right) + \left( -15\right) = \\ &= 40x^2 + 100x + \left( -6x\right) + \left( -15\right) = \\ &= 40x^2+94x-15; \end{aligned} $$

Polynomial Operations Calculator