Let's break down and solve the expression step by step:

$(8 - 2^3) + 21$

1. Exponentiation: Solve $2^3$ first: $2^3 = 2 \times 2 \times 2 = 8$

2. Subtraction: Now, substitute $2^3 = 8$ into the expression: $(8 - 8) + 21 = 0 + 21$

3. Addition: Finally, add 0 and 21: $0 + 21 = 21$

So, the result of the expression is: $\boxed{21}$

Would you like more details on any step?

Here are 5 related questions to further explore:

1. How would the answer change if the exponent were different, e.g., $2^4$ instead of $2^3$?
2. What happens if you reverse the subtraction to $8 + 2^3$?
3. How does the order of operations impact the result if the expression were written differently?
4. How would the result change if the constant 21 were replaced by another number, like 30?
5. What if you had to solve $(x - 2^3) + 21 = 0$ for $x$?

Tip: Always handle exponents before any other operations according to the order of operations (PEMDAS: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction).