Let's simplify the given expression step by step:

Given: $6(6a - 7a - 1) - 4a$

1. First, simplify the terms inside the parentheses: $6a - 7a = -a$ So, the expression becomes: $6(-a - 1) - 4a$

2. Now, distribute the $6$ across the terms inside the parentheses: $6(-a) + 6(-1) = -6a - 6$ So, the expression becomes: $-6a - 6 - 4a$

3. Combine like terms: $-6a - 4a = -10a$ So, the final simplified expression is: $-10a - 6$

Thus, the simplified expression is: $\boxed{-10a - 6}$

Would you like more details on any step or further explanation?

Here are 5 related questions to deepen your understanding:

1. How do you distribute a number across terms inside parentheses?
2. What is the importance of combining like terms in algebra?
3. How can you apply the distributive property in reverse?
4. How would the expression change if there were positive terms inside the parentheses?
5. How can you factor the final expression?

Tip: Always simplify inside parentheses first before distributing.