if you are given 2 pointx X & Y that are 6 centimeters apart, how many points exist which are equidistant from both X & Y and also 3 centimeters from point X? How do I calcuate this - I think I would draw 2 perpendicular lines where X & Y are 6 Cent. Apart on one of the lines I drew and 3 cent from these 2 points so I only came up with one point.

I don't know the math involved, but common sense says you are correct.
Any number you could place in the spot of the 3, and your answer could range anywhere from zero, to infinity, depending on the number of decimal points involved. Infinite decimal points could range the answer to your question to infinity, even if the three were only 3.000000000000000000000000001. On the other hand, if the spot of the three were to be represented by 2.999999999999999999999999999999999999999999999999 99, your answer could only be zero.

this link may help you out (http://hsc.csu.edu.au/maths/teacher_resources/2384/prof_reading/journals/tayler/tayler.htm)

Yup, you'll get only one point, good job!:)