Answer:
D. 112°
General Formulas and Concepts:
A line is always 180°.
Order of Operations: BPEMDAS
Explanation:
Step 1: Set up equation
m∠ABD + m∠DBC = m∠ABC
(3x + 10) + (2x) = 180°
Step 2: Solve for x
- Combine like terms: 5x + 10 = 180
- Subtract 10 on both sides: 5x = 170
- Divide 5 on both sides: x = 34
Step 3: Find m∠ABD
m∠ABD = 3x + 10
- Substitute: m∠ABD = 3(34) + 10
- Multiply: m∠ABD = 102 + 10
- Add: m∠ABD = 112°