What's a 6.9? I'm very confused o_O

Which graph represents the parent function of y=(x+2)(x-2)

What is the volume of a cone with a height of 6 cm in the radius of 2 cm

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