短文改错My math teacher is used to kake off his overcoat as soon

短文改错My math teacher is used to kake off his overcoat as soon as he comes into the classroom.
After that ,he willask someone answer a question.
Instead of giving the answeres,he let us solve the problem on his own,He always gives a clearly explanation of the method,and introduches many approaches to the problem.At the first ,our class's math performance was bettter than of the other class.
However ,with his help ,we caught up with them .In addition,he always keeps hia wards.
He used to promise us as we could perform well ,he would buy us a drink .As a result ,
we achieved our goals and he did that he said.