Sampling is ordinarily used when the number of items comprising the population is relatively small.

I believe this statement is false, and that sampling is used when the number of items in a population are fairly large. One would use a sample to represent some form of measurement or test so that it can be applied to the larger number of same objects.

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.