Simplify:
(x+3)(x-3)-(1-9)

Find the value of the cosine for angle a

Solve for x: 5/3 x = 20/21 it's fraction. remember to simplify your fraction

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