then you will multiply 9×-2, which will equal -18. the 18 stays negative because when multiplying a (+) and a (-) your answer will always be a negative. That's how I got the answer!
The given interval is from 2 onto infinity, basically describing everything larger than 2. We do not include 2 as part of the interval because of the curved parenthesis. If you had then you would include 2 and you would say
In set builder notation, we can write which is basically a more long-winded way of saying . The fancy looking R indicates that x is a real number. So it's saying "we have a set of real numbers such that these numbers are greater than 2".