Let's simplify the expression:

$-3x(-9x + 7) + (x^2 + 2x - 8)$

Step 1: Distribute $-3x$ across $(-9x + 7)$

$-3x(-9x) + (-3x \cdot 7)$

This gives:

$27x^2 - 21x$

Step 2: Rewrite the expression with the distributed terms

$27x^2 - 21x + (x^2 + 2x - 8)$

Step 3: Combine like terms

$(27x^2 + x^2) + (-21x + 2x) + (-8)$

$28x^2 - 19x - 8$

Thus, the simplified expression is:

$28x^2 - 19x - 8$

Let me know if you'd like more details or have any questions.

Here are 5 related questions to deepen your understanding:

1. How would the expression change if the coefficient of $x$ in $-9x + 7$ was different?
2. What happens if you change the sign of the whole expression?
3. Can you factor the final result $28x^2 - 19x - 8$?
4. How does distributing a negative number affect the terms inside parentheses?
5. What is the impact of changing the signs inside the second parenthesis $(x^2 + 2x - 8)$?

Tip: Always distribute negative signs carefully to avoid mistakes in the final answer.