They make him do math exercises for two hours every day.
被动语态→He is made to do math exercises for two hours every day.
英语中,不少动词都用动词不定式作宾语补语,构成复合宾语,如：
The parents teach the boy to be polite to people.
在make,let,have,see,watch,feel,notice 等动词后的的复合宾语中,不定式都不带to,如：
We saw the man beat the young boy.
但这种句子如果变为被动语态,就不能不要to,如：
被动语态→ The man was seen to beat the young boy.
提问中的句子就是这种情况.
欢迎提问,