The perimeter of the rectangle is 40m. what is the length of the missing side?

The sides could be 10 by 10, 2 by 18, or many others.

Hello!

A valid sample is a sample where everyone has a chance to answer

This is not valid because it was only the first three people not random selection

The answer is A) It is not a valid sample because it is not a random sample of the population.

Hope this helps!