Question

2/3 of the pupils in a hall are boys and the rest are girls. 1/4 of the boys and 1/3 of the girls wear spectacles. what fraction of the pupils in a hall does not wear spectacles?

Answer 1

1/4 * 2/3 + 1/3 * 1/3 wear
1/6 + 1/9 wear
3/18 + 2/18 wear
5/18 wear
so
13/18 do not wear