lǎo / shī / zhèng / zài / jiǎng / jiě / bù / kě / shǔ / míng / cí / qián / miàn / bù / néng / zhí / jiē / shǐ / yòng / shù / zì / de / guī / zé

老师正在讲解不可数名词前面不能直接使用数字的规则。

The teacher is explaining the rule that numbers cannot be used directly before uncountable nouns.