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

$$ \begin{aligned} P(x) &= 3r-4 \\ Q(x) &= 7r-2 \\ \end{aligned} $$

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

$$ \begin{aligned} \left( \color{blue}{ 3r-4}\right) \cdot \left( \color{orangered}{ 7r-2}\right) &= \underbrace{ \color{blue}{3r} \cdot \color{orangered}{7r} }_{\text{FIRST}} + \underbrace{ \color{blue}{3r} \cdot \left( \color{orangered}{-2} \right) }_{\text{OUTER}} + \underbrace{ \left( \color{blue}{-4} \right) \cdot \color{orangered}{7r} }_{\text{INNER}} + \underbrace{ \left( \color{blue}{-4} \right) \cdot \left( \color{orangered}{-2} \right) }_{\text{LAST}} = \\ &= 21r^2 + \left( -6r\right) + \left( -28r\right) + 8 = \\ &= 21r^2 + \left( -6r\right) + \left( -28r\right) + 8 = \\ &= 21r^2-34r+8; \end{aligned} $$

Polynomial Operations Calculator