1. Stating the problem: Simplify the expression (a) $3x - \{5 - [8 - (5x - 4)]\}$. 2. Use the order of operations and simplify inside the brackets first. 3. Simplify the innermost bracket: $(5x - 4)$ remains as is. 4. Simplify $8 - (5x - 4) = 8 - 5x + 4 = 12 - 5x$. 5. Now simplify $5 - [12 - 5x] = 5 - 12 + 5x = -7 + 5x$. 6. Finally, simplify $3x - (-7 + 5x) = 3x + 7 - 5x = -2x + 7$. Final answer for (a): $-2x + 7$.