To simplify the given expression:

$(2x - 3y) - (8x + 6y + 4)$

1. Distribute the negative sign through the second parentheses:

$= 2x - 3y - 8x - 6y - 4$

2. Combine like terms:

$= (2x - 8x) + (-3y - 6y) - 4$

$= -6x - 9y - 4$

Thus, the simplified expression is:

$-6x - 9y - 4$

Would you like a more detailed breakdown of the steps or have any questions? Here are some related questions:

1. How would you simplify the expression $(4a + 5b) - (2a - 3b + 7)$?
2. What happens when you have multiple sets of parentheses to simplify?
3. How do you factor the expression $-6x - 9y - 4$?
4. How do you distribute negative signs in algebraic expressions?
5. What are like terms, and why do we combine them?

Tip: When distributing a negative sign, be sure to change the signs of all the terms inside the parentheses.