The question does not seem complete, but I'll represent the statement mathematically and look for their ages each. This is because the worst they can ask for is their ages.
Let C stand for Courtney's age, A for Andrei's age, N for Natalie's age and S for Shari's age. From the question we can deduce the following:
An x-coordinate is the x value in an ordered pair, which is just two mathematical objects, such as numbers, paired together. Usually, the x-coordinate is the first number in that pair. For instance, in the ordered pair (2,5), the x-coordinate would be '2.
