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

$$ \begin{aligned} P(x) &= 2x+3 \\ Q(x) &= 8x+1 \\ \end{aligned} $$

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

$$ \begin{aligned} \left( \color{blue}{ 2x+3}\right) \cdot \left( \color{orangered}{ 8x+1}\right) &= \underbrace{ \color{blue}{2x} \cdot \color{orangered}{8x} }_{\text{FIRST}} + \underbrace{ \color{blue}{2x} \cdot \color{orangered}{1} }_{\text{OUTER}} + \underbrace{ \color{blue}{3} \cdot \color{orangered}{8x} }_{\text{INNER}} + \underbrace{ \color{blue}{3} \cdot \color{orangered}{1} }_{\text{LAST}} = \\ &= 16x^2 + 2x + 24x + 3 = \\ &= 16x^2 + 2x + 24x + 3 = \\ &= 16x^2+26x+3; \end{aligned} $$

Polynomial Operations Calculator