Please provide an explanation. Thanks

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)

Identify all the cases where non-probability sampling is used when attempting to study the characteristics of a large city. studies on every subject in the population divide a population in groups and obtain a sample studies with a limited amount of time demonstrate existing traits in a population studies with the nth person selected

M∠cbd=4x+52∘ m∠abc=8x−10∘\qquad m \angle abc = 8x - 10^\circm∠abc=8x−10∘ find m∠cbdm\angle cbdm∠cbd: