What's the answer to question number

What is this inequality notation? t is less then or equal to 2

Find the nonpermissible replacement for binthis expression.b2/5b +5

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