Answer:
23
General Formulas and Concepts:
Pre-Algebra
Order of Operations: BPEMDAS 
- Brackets 
 - Parenthesis 
 - Exponents 
 - Multiplication 
 - Division 
 - Addition 
 - Subtraction 
 
Algebra I
Explanation:
Step 1: Define
g(x) = x² - 4
f(x) = -2x - 3
g(-6) is x = -6 for function g(x)
f(-6) is x = -6 for function f(x)
Step 2: Evaluate
g(-6)
- Substitute in x: g(-6) = (-6)² - 4
 - Exponents: g(-6) = 36 - 4
 - Subtract: g(-6) = 32
 
f(-6)
- Substitute in x: f(-6) = -2(-6) - 3
 - Multiply: f(-6) = 12 - 3
 - Subtract: f(-6) = 9
 
g(-6) - f(-6)
- Substitute: 32 - 9
 - Subtract: 23