Answer: 
x = -8 
m∠BDC = 68° 
General Formulas and Concepts: 
Pre-Algebra 
Order of Operations: BPEMDAS 
- Brackets 
- Parenthesis 
- Exponents 
- Multiplication 
- Division 
- Addition 
- Subtraction 
Equality Properties 
Geometry 
- Definition of a Line: A line is 180° 
Step-by-step explanation: 
Step 1: Set up Equation 
m∠BDC + m∠CDA = 180° 
(-7x + 12)° + (-8x + 48)° = 180° 
 
Step 2: Solve for x 
- Combine like terms: -15x + 60 = 180
- Isolate x term: -15x = 120 
- Isolate x: x = -8 
Step 3: Find m∠BDC 
- Define: m∠BDC = (-7x + 12)° 
- Substitute in x: m∠BDC = (-7(-8) + 12)° 
- Multiply: m∠BDC = (56 + 12)° 
- Add: m∠BDC = 68°