Answer:
Hello There. ☆°~-----__▪●▪__-----~°☆
If points A, D and C lie on a straight line, then angles ∠ADB and ∠BDC are supplementary angles and
m\angle ADB+m\angle BDC=180^{\circ}.
1. If you move point B right from the initial position, then m∠ADB increases and m∠BDC decreases, but m\angle ADB+m\angle BDC=180^{\circ}.
2. If you move point B left from the initial position, then m∠ADB decreases and m∠BDC increases, but m\angle ADB+m\angle BDC=180^{\circ}.
3. When point B lie on the line ADC, then:
a. Point B lies on the right hand from point D: m\angle ADB=180^{\circ} \\m\angle BDC=0^{\circ} ;
b. Point B lies on the left hand from point D: m\angle ADB=0^{\circ} \\m\angle BDC=180^{\circ} .
4. When point B is reflected about the line ADC situation is the same as in parts 1 and 2.
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ItsNobody~ ☆
