Pls help it is due today

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

Paper plates cost $8 per package and plastic utensils cost $5 per package. your supplier delivers 15 packages for a total cost of $90.

What is the value of x in the equation 1/5x - 2/3y = 30 , when y = 15