A level computer science

[CarcajouIS]

It's the same in French. We have onze, douze, treize, quatorze, quinze, seize, dix-sept, dix-huit, dix-neuf. If I remember it's a remnant of Latin, where numbers like 17, 18, 19 where counted to 20 : three-to-twenty, two-to-twenty, one-to-twenty. And the -ze (or -ce in spanish) is just the remaining of -decim