Given the equation:

$y(x - 8)$

Substitute $x = 12$ and $y = 5$ into the equation:

$5(12 - 8)$

First, simplify inside the parentheses:

$5(4) = 20$

So, the result is $20$.

Would you like more details or have any questions?

Here are 5 related questions:

1. What happens if $x$ is negative in this equation?
2. How does the result change if $y$ is a fraction?
3. Can you solve the equation for $x$ if the result is given?
4. What is the geometric meaning of this equation?
5. How would this change if $x$ or $y$ were complex numbers?

Tip: Always perform operations inside parentheses first when simplifying an expression.