There are 33 countries where the mean mathematics score is at least 10 test points ahead of Wales, and 28 countries where the mean mathematics score is at least 10 test points lower.
Mae sgôr cymedrig 33 gwlad ar gyfer mathemateg o leiaf 10 pwynt prawf o flaen Cymru, ac mae sgôr cymedrig 28 gwlad ar gyfer mathemateg o leiaf 10 pwynt prawf yn is.