1. Teacher Chen teaches Chinese, Teacher Zhang teaches math and Teacher Li teaches English.

2. Teacher Chen teaches Chinese, Teacher Zhang teaches English and Teacher Li teaches mathematics.

Teacher Chen teaches mathematics, teacher Zhang teaches Chinese and teacher Li teaches English.

Teacher Chen teaches mathematics, teacher Zhang teaches English and teacher Li teaches Chinese.

5. Teacher Chen teaches English, Teacher Zhang teaches mathematics and Teacher Li teaches Chinese.

6. Teacher Chen teaches English, Teacher Zhang teaches Chinese and Teacher Li teaches math.

To sum up, a * * * has six teaching situations.

In the arrangement problem, generally speaking, taking out m(m≤n) elements from n different elements and arranging them in a certain order is called the arrangement of taking out m elements from n elements. In particular, when m=n, this arrangement is called full arrangement.

On the classification of arrangement:

1, there are two kinds of arrangement: sorted arrangement and full arrangement. When m different elements are taken out from n different elements, when m

2. The arrangement of m elements among n elements can be regarded as m ordered subsets of a set consisting of these n elements, so the number of m ordered subsets of a is P(m, n).