Answer:
k = 8
General Formulas and Concepts:
Pre-Algebra
Order of Operations: BPEMDAS 
- Brackets 
- Parenthesis 
- Exponents 
- Multiplication 
- Division 
- Addition 
- Subtraction 
Equality Properties
Explanation:
Step 1: Define
-84 = -2(2 + 5k)
Step 2: Solve for k
- Divide -2 on both sides: 42 = 2 + 5k
- Isolate k term: 40 = 5k
- Isolate k: 8 = k
- Rewrite: k = 8
Step 3: Check
Plug in k into the original equation to verify it's a solution.
- Substitute in k: -84 = -2(2 + 5(8))
- Multiply: -84 = -2(2 + 40)
- Add: -84 = -2(42)
- Multiply: -84 = -84
Here we see that -84 does indeed equal -84.
∴ k = 8 is the solution to the equation.