The first positive odd number is 1, the second positive odd number is 3, the third positive odd number is 5, and so on. We can see that each odd number is 2 more than the previous odd number.
Therefore, to find the tenth positive odd number, we can start with the first positive odd number (which is 1) and add 2 to it nine times, since we want the tenth odd number:
1 + 2(9) = 1 + 18 = 19
Therefore, the tenth positive odd number is 19.