DRUG CLASS AND MECHANISM: Rosuvastatin is an oral drug for lowering blood cholesterol levels. It belongs to a class of drugs called HMG-CoA reductase inhibitors, more commonly referred to as  statins ..RUG CLASS AND MECHANISM: Rosuvastatin is an oral drug for lowering blood cholesterol levels. It belongs to a class of drugs called HMG-CoA reductase inhibitors, more commonly referred to as  statins ..
Natural numbers are naturally used for counting apples (and other things) so they are sometimes called counting numbers. Even some animals other than humans can count and add, so they must be natural. Minus two apples isn't very natural so negative numbers are not included.
So to accommodate subtraction, and to be able to represent amount owed by numbers, we extend the natural numbers to include the numbers 0 and the negatives of the natural numbers. This entire set of numbers, positive natural numbers, their negatives and 0 is called the set of integers, and is denoted by the letter Z. We can take any two members of Z and add them or subtract them and in either case get another member of Z. I know all that, but I am very rusty on actual additions and subtractions.