Easy enough, and counting higher than 10 has a fairly regular pattern.
Xoa for eleven is simply ten plus one, and so on until you get to 19, Xonai. Once you get to the twenties you use a slightly different structure. Tuxoa for 21 is two times ten plus one. This continues until you get to ninety-nine, naixonai.
100 has it's own name, haku, but structure remains relatively the same.
Once you get to numbers this high sometimes hyphens make it easier to read. For example naihakunaixonai could be written as naihaku-naixonai. This is not required, it simply makes it quicker to read.